petrol in diesel
I was reminded the other day of a misfuel that we were called out to resolve for a professor at the University of Brighton.
Our learned friend had tried to run a diesel Audi A3 on a mix of 25% unleaded, 75% diesel and 100% optimism. Obviously the vehicle rejected this kind of treatment and decided to go on strike by refusing to start.
Somehow or other he had managed to get the vehicle to the university campus and it sat looking very sorry in an empty parking lot after hours. Our engineer arrived and, as usual, drained the fuel from the tank. When he opened the bonnet to access the fuel lines to clear and clean the pumps, lines and filter he found things to be slightly amiss.
Apparently it turned out that the professor had attempted to drain out the fuel himself. Because he was not able to bypass the anti-syphon on the filler neck into the tank he figured he would be able to retrieve the fuel from the engine.
Now, I don’t know what this Einstein had majored in at university, but it certainly wasn’t anything to do with mechanics or vehicles. His solution for not having the correct tools to be able to remove the fuel lines was to improvise. Our engineer was quite surprised to find that all the fuel lines in the engine had been very neatly cut with a surgical knife and that the customer had tried to suck the fuel out of these.
The most amazing part of the story was that the customer was taken aback by our engineer telling him that cutting his fuel lines certainly wouldn’t help the vehicle to run once the contaminated fuel had been drained.
Fortunately our man had some spare fuel lines in the back of the van and managed to fit these onto the Audi. Once done with this, he fully drained the system and got the vehicle running again.
I guess the moral of the story is: if you don’t know how to get petrol out of your diesel car, DON’T TRY. Call the professionals!
I had decided that I should have a nice quite Sunday to help me recover from the hectic week. Why is it that every time I try to relax it never works out?
Sunday morning for me started bright and early. In fact, by 10am I already had five of our engineers out on the road to help stranded motorists. There was the diesel Land Rover Freelander just outside Canterbury whose owner had tried to run on petrol; a misfueled BMW 118 (beautiful car) down the road from Gatwick; a brand new Alfa Giulietta that was stuck at on a petrol station forecourt in Tenterden, Kent; and a Nissan X-trail and Ford Mondeo – both in Dunfermline, Scotland – which had been filled with diesel instead of petrol.
As if that wasn’t enough to keep me busy on a Sunday the rest of the day seemed to follow the same suit.
We also attended and did full fuel drains on the following vehicles – all of which had been filled with petrol instead of diesel:
- Land Rover Discovery 3 in Bramley
- VW Golf in Crystal Palace
- BMW X3 in Woodford Green, London
- Toyota Land Cruiser in Pitlochry, Scotland
- Toyota Avensis in Edinburgh
- Peugeot 207 in Maidstone
- Peugeot 407 in Romford
- VW Transporter in Brighton
However, probably the most interesting job of the day was an old Ford Transit that had been converted into a Horsebox. The lady driving the vehicle had filled it to the brim with unleaded. Needless to say she should have been using diesel. When the vehicle broke down on the side of an Edinburgh road the lady was very fortunate to have an alternate means of transport in the back. She went off for a little ride while we drained and cleaned her Ford. By the time she was back it was up and running again so she could be off to her horse meet.
So, all in all, quite a hectic day for a Sunday and I obviously didn’t get the rest and relaxation that I was looking forward to.
If you’ve just put petrol in a diesel car I’m sure that first thing you want is sound advice on what to do next. There are a lot of opinions out there on how you should treat your vehicle after a misfueling, and to be honest, most of it is worthless. My knowledge on the subject is a result of extensive experience dealing with misfueled vehicles. I have spoken with many tens of thousands of motorists who have put petrol into their diesel vehicles, and a few thousand who have put diesel into petrol. Additionally, as a company we have completed fuel drains on many, many thousands of misfueled vehicles. This is our business and is pretty much the only thing we do – therefore we are professional specialists on the subject. With all that in mind, I’m going to give you some advice on what to do and what the common untruths are.
I’ve filled up my car with petrol instead of diesel and drove it until it conked out. Have I ruined it?
It is very unlikely that you have ruined your car by misfueling and driving it. That said it’s not unheard of for a pump to fail, or an injector to get clogged. But, statistically speaking, of the more than 4,000 fuel drains we have done so far this year on run misfueled vehicles, less than 10 had sustained damaged necessitating a visit to a garage for repair (less than 0.25%). In the cases of damage the vehicles had generally been run continuously, long after the misfuel was known about, and the customers had tried to just “get away with it”.
I’ve misfueled my vehicle and the dealership has told me I need to replace almost the entire fuel system. Is this true?
No. Well, if it’s not true why do people say it? The answer to that is very simple – money. If you put petrol into your diesel Mercedes, for example, and take it in to the dealership you would likely be faced with a bill to the tune of thousands of pounds. Mercedes will say that because there is a possibility that some parts have become damaged (regardless of how remote that possibility is) they are no longer able to guarantee those parts. Therefore, in order for them to be able to maintain your warranty and continue to guarantee your engine parts they will need to replace them. Not only does this protect them from an unsatisfied customer suing when their engine fails it also makes them a tidy little sum of money.
A few months ago we did a fuel drain on a brand new Mercedes C Class. The customer had put petrol into it and then moved it from the pump to a parking bay at the petrol station. It was then recovered to the dealership and he was given a bill for £750 to drain the fuel out and £9,000 to replace the “damaged” engine parts. We attended the vehicle, drained it and cleaned it out for the customer for a tiny fraction of that amount. I spoke with the customer recently and he has had absolutely no problems with the vehicle at all. So, did he really need to have everything replaced? I leave that for you to decide.
I’ve only put a little petrol into the diesel tank, less than 10% of the fuel tank’s capacity. Can I just top it up with the correct fuel?
You hear a lot of this going around. And you also hear a lot of conflicting stories and opinions on its validity. There are probably as many correct answers to this as there are cars in the world. I’ve heard of people having a 10% contamination problem and filling the vehicle up and never experiencing a problem at all. I’ve also been called out to help stranded motorists who put less than 5% petrol in their diesel and the vehicle conked out. I think I can best explain it with an analogy: Liken misfueling to putting drugs into the body. Pretty much everyone reacts differently to drugs. Some can have a little with no serious adverse effects. Some can’t handle even the smallest amounts. Anyone will die if you give them too much.
So, when deciding whether to “fill it up and give it a go”, just realise that it’s a gamble. How lucky do you feel?
If you are still unsure of what to do after putting petrol into your diesel car, give us a call. We’d be glad to help.
What’s the most common thing I hear when our unlucky customers call to ask for a fuel drain after having put petrol into their diesel, or diesel into their petrol? Almost one for one they tell me that they can’t believe that they’ve misfueled and they are deeply embarrassed and annoyed
If you’re reading this it’s probably because you’ve done the same thing and are probably feeling the same way. Well, I thought I would share a little anecdote with you which might help to mitigate the pain and suffering you feel by making you realise that literally everyone is susceptible to misfueling.
Who would you think is least likely to misfuel their vehicle? Surely it would be a fuel drain technician. Well, that’s exactly what one of our technicians did a few months ago. He’s probably going to hate me for putting this up on the website but I thought his misfortune might just help to ease the suffering of others.
Basically, he’d just completed a full fuel drain on a customer’s car at a petrol station in south London. He decided to top up before heading home and you can guess the rest. It’s quite a sight to see a Fuel Fixer Ford Transit’s fuel drain pumps cleaning out its own tank. What an advert for us!
So, if you’ve misfueled your vehicle by putting petrol in your diesel or diesel in your petrol, give us a call. We really do understand that it can happen to anyone.
Being a vet in Cumbria is a busy job. It is a county with a lot of sheep, cows, horses as well as cats and dogs and the other animals that make up the patient lists of such people.
So it isn’t unusual to find a vet going about his business in a Land Rover. But it is quite unusual to find one stranded in a Land Rover because the vehicle refuses to run on a mixture of diesel and petrol. This is what a fuelfixer technician found when he arrived to perform a fuel drain after a call from a local farmer.
The vet was anxious to get going as fast as possible so he could pay a visit to a local cow called Shirley.
He needn’t have worried. The technician had the vehicle drained, cleaned and refuelled within 45 minutes – another tale of the heroism of our technicians.
Whether you are going to or coming from a visit with a cow by whatever name in Cumbria you can be assured of similar service just as the following people did in recent times;
Other incidents of a similar nature in Cumbria are;
Petrol in Diesel in Carlisle on a Kia, £67 petrol
Petrol in Diesel in Ulverston on an Jaguar S, type £5 petrol
Petrol in Diesel in Barrow-in-Furness on a on a Toyota Avensis, £20 petrol
Petrol in Diesel in Seascale on a Rover 75 with £30 of petrol
Petrol in Diesel in Whitehaven on a Volvo, 45 litres of petrol
Petrol in Diesel Workington on a Vauxhall Vectra, £90 worth of petrol
Petrol in Diesel in Wigton on a on a Vauxhall Viva 30 litres petrol
Petrol in Diesel in Keswick on a Volvo £67 petrol
Petrol in Diesel in Kendal on a Skoda with £30 of petrol
Petrol in Diesel in Penrith on a Subaru, 45 litres of petrol
A machinist driving from Slough to Reading filled his diesel tank with petrol on the way home from the pub. Petrol in diesel is not good for combustion and his car soon came to a stop.
With nightmare visions of his Fiat being towed to the Fiat dealer and of the horrendous bill that would inevitably ensue he proceeded to worry. Needlessly as it happened because this is exactly the sort of situation that Fuelfixer was set up to fix. How this turned out for the machinist we have no idea because he was unable to get on the internet and search for a solution. Instead he left his car at the side of the road and the next day called his Fiat dealership.
If he had called us we would have had a technician arrive within an hour with his own nice van kitted out with every possible tool that might be needed to handle petrol in diesel in a huge variety of cars. Our technician would have drained the nasty petrol out of his tank and out of his fuel system within 29.4 minutes (average calculated time this job takes throughout the UK in the last year). Then he would have loaded in some nice clean diesel into the tank. The machinist would then have found his trusty Fiat a goer once again.
Fortunately for other motorists we are often found and have helped many other stranded motorists in Berkshire. For instance;
Petrol in Diesel in Newbury on a Ford Escort
Petrol in Diesel in Reading on a Skoda
Petrol in Diesel in Slough on a Kia
Petrol in Diesel in Bracknell on a Ford Focus
Petrol in Diesel in Streatley on a Fiat
Petrol in Diesel in Lambourn on a Jaguar S type
Petrol in Diesel in Theale on a Honda Accord
Petrol in Diesel in Pangbourne on a Seat Ibiza
Petrol in Diesel in Reading on a Volvo
Petrol in Dieselin Slough on a Suzuki
Petrol in Diesel in Newbury on a Subaru
A cinematographer making a film on the delights and tourist attractions of Luton in Bedfordshire ensured his place in history by putting £5 of petrol in the empty diesel tank of his Saab 900. I don’t really have much to say about it other than when our technician arrived to drain his tank, clean the lines and put fresh diesel in, he became the star of the movie. It will be out on general UK wide release sometime in the spring of next year.
Being a leaping gnome with long hair the technician never expected to be a star but there it was. He has become quite obnoxious as a result but he does do good work in the field of dealing with the problems of putting the wrong fuel in vehicles designed for the right fuel only.
The same technician has been known to deal with petrol in diesel problems in other parts of Bedfordshire. Such as;
Bletchley – the mystery of how £700 of petrol got into a tank barely holding 50 litres.
Between Dunstable and Hemel Hempstead an old lady in a Morris Minor had put 20 litres of petrol in her petrol tank but thought she had really had a diesel tank. What he did in that instance is anybody’s guess.
Of course Milton Keynes has to be a place where he goes quite frequently to remove petrol in diesel from vehicles belonging to economists, if Keynes can be called such.
Leighton Buzzard is a really odd name for a small town in Bedfordshire but it does get its fair share of petrol in diesel cases to which our intrepid technician is always happy to handle.
Bedford itself also happens to be in Bedfordshire and there are several people there who put petrol in diesel tanks, it seems, as a matter of course.
Other cases in the same area include;
Petrol in Diesel in Hemel Hempstead on a BMW 5 series
Petrol in Diesel in Dunstable again on the same BMW 5 series. This time it was the wife.
Petrol in Diesel in Luton on a Mercedes with over £100 of petrol in the tank!
Petrol in Diesel in Bletchley on a Corvette
Petrol in Diesel in Leighton Buzzard – two women having the most amazing argument as to who was to blame for Labour losing the last election.
Petrol in Diesel in Berkhampstead on an Enigma
Petrol in Diesel in Harpenden
This is a question allot of people ask if they are unsure of whether or not they have put the wrong fuel in the car.
The answer differs greatly, some cars die before they leave the forecourt, some can drive for 200 miles or even more but refuse to start again from cold, it is best answered by giving you the facts and you can work it out yourself
1) when you misfuel the percentage of wrong fuel matters, the more wrong fuel generally the early the engine refuses to run
2) there is between 500ml and a litre of fuel in the filters and pumps, after misfuelling when you start the engine it will be running on the clean fuel in the system that you had when you arrived at the pump, this can take between 10 seconds and 10 minutes to effect the engine
3) on an already hot engine many diesel cars will drive (albeit rough) with petrol in them, the problem starts when the car is left overnight and refuses to start in the morning, flat batterys after a misfuel is a common occurance from people trying to start the car not knowing they have misfueld.
4) the type of engine matters, sophisticated highly tuned diesel’s are more sensitive to fuelling issues, the sporty volkswagon diesels in particular – but they recover fine after a fuel drain
5) driving at a steady speed with misfuel will get you further than stop start traffic, this is not always the case but what i have seen suggests it
6) taking any chances is not worth the risk, if you misfueld would you rather get your car drained down on a well lit petrol station forecourt with ample supplies of coffee and cake whilst you wait 45 minutes for a fuel drainer to arrive – and be on the road in 30 minutes after he arrives , or take the chance of sitting by the side of the road broken down at neither a place or time of your choosing whilst waiting for a recovery vehicle?
7) If you have any doubt you have misfueld or put petrol in your diesel its well worth carrying out an olfactory test, go on have a sniff! if your diesel tank smells like petrol – even just a wincy bit then it is
hope that helps
Having drained the wrong fuel from thousands of cars I have spent more time on petrol station forecourts than most.
Every wrong fuel removal involves putting a flexitube into a fuel tank and letting a pump do its thing, on a corsa with 5 litres this may take 5 minutes, a rangerover with 100 litres of wrong fuel in it, or an Iveco van may take an hour, there’s not much to do in this time other than monitor the fuel system and chat with the customers, in between daydreaming I find myself playing the “how much game”, thats where I watch cars coming into the petrol station and try and guess how much they will fuel they will buy before they pump, different stations have different clientele, BP M&S for example tends to have a higher spending customer who will often fill the tanks up, it surprises me still how many people fill up with fivers and tenners – which must be a daily fill up.
I cant stand filling up, so when I do its always to the top from empty, but next time your in a petrol station look at the pumps and see what the last sale was, it would give you a fairly good idea of the clientele of the petrol station and the area your in
There’s also a loyalty to specific stations, some people turn up at the same time and place every week for the top up, and often misfuel when they go off the beaten track and try somewhere new. ive done the same car 3 times in two months in the same station that had been misfuelld, always on a friday night after she had done her weekly shop, I didnt have the heart to charge for the 2nd and 3rd drains but it still cost her 2 full tanks of wasted fuel, I havent seen here for a while and fingers crossed she has learnt her lesson
Had a call from a distraught lady yesterday who had put petrol in her diesel BMW x5, she had it recovered to the dealership last week and after 4 days got the “estimate” in – £6500.
It wasent the highest repair quote I have heard for repairing a misfuel but it was still a bit steep – considering the work didnt need done.
A bmw engine is no pansy, capable of operating in temperatures from -30c to +50, running for 250.000 between major rebuilds, and lasting for 20 years pushing a heavy car body at high speed – does not have an in built “self distruct” function when it detects petrol in a diesel engine.
Misfuelling is a common occurrence and happens all the time, it is a myth that petrol will destroy your diesel engine or that common rail components need replaced.
In the case of the Lady in west london she had been told that major work was needed including replacing fuel tank, hoses, high pressure fuel pump, in tank pump, piezo injectors etc, all not needed.
I met her at the dealership (where I have done 4 similair drains on misfuelld BMW’s) and the dealer staff were helpful and let me do the fuel drain in the premises, it took all of 35 minutes and after a flush and filling up with the wrong fuel she drove away in her beloved x5.
Fuel drains are the way forward, the AA and RAC both have a large fuel draining fleet and they wouldnt be in the business if it opend them up to liabilities further down the line.
The truth is cars can deal with a misfuel, it doesnt kill them or destroy the engines or pumps, its not great for the tank, and can corrode hoses and internal rubbers if left for too long but it doesn’t cause the catastrophes that the dealers would like you to believe.
If you have misfuelled a car and it is in the dealers it not too late to get a fuel drain, and dont get taken in by empty threats of warranty invalidation, you can always quote the Eu Block Exmption Rule which put an end to the dealers shady practices of adding clauses to warrantes on cars to nobble consumers.
thats about enough from me
I have done a few fuel drains on Fiats recently so if you have put the wrong fuel in your Fiat Panda or unleaded In your Doblo or diesel in your petrol 500 – we can help.
Fiats are easy cars to perform fuel drains, being front wheel drive they have simple fuel tank set ups and are easy to access.
Fiat has a some great little diesel cars out at the moment, and I like working on them. this particular fiat that I did had been hire from choices vehicle rentals and the client had
If you have misfueld your fiat give me, or any other mobile fuel drainer a call and you will be back up and running again in an hour or so.
For instructions on how to do a diy fuel drain, providing you have the know how and a safe place to do it I would suggest going in through the back seat, this is done as follows on most fiat models
1) lift up back seat, this unclips with a hard tug (a proper hard tug – I,e a man tug)
2) unscrew the big steel collar holding the take sender, this is always so much easier if you read the direction arrows and loosen it in the direction indicated, try as you might you cannot take it off by tightening it.
3) disconnect fuel lines and electrical sender
4) lift out in tank fuel pump and put your own hose into the tank to take out the mixed fuel
5) once empty put it all back together again
Only perform a DIY fuel drain if you are technically minded and fully aware of the forces of Darwinism at work when working with highly volatile, flammable and explosive nature of petrol.
For the sake of safety mixed fuel should be treated as PETROL no matter what the quantity involved, petrol is a different animal than diesel and creates an explosive vapour in temperatures above 5c (thats cold)
Hope that helps, call me if your stuck or something with a blue flashing light if it goes totally tits up.
Does petrol float on top of diesel? or does diesel float on top of petrol?.
Petrol weighs 737.22 grams per litre, (water weighs 1000 grams per litre)
Diesel weighs 840 grams per litre.
When diesel and petrol mix they blend and cannot be separated by taking fuel off the top or bottom.
when you put the wrong fuel in a vehicle it mixes in no particular order, some may say that the diesel will go to the bottom or the petrol will float harmlessly on top, have been dealing with mixed fuel as long as I have I can assure you this is not the case
I have had my mixed fuel tested a few times and had samples taken from the bottom and top of the storage tanks after they had sat for several weeks, the mixed fuel taken from the top is more “petroly” but still has allot diesel in it, and the mixed fuel at the bottom is more “diesely” but again has petrol in it.
If you have mixed fuel in the tank of your car do not assume that there is a higher or lower portion of anything at the bottom where it feeds into the pump, for one thing the fuel pumped in will be cold, the fuel in the car will be warm from the return line heat, when you put new fuel in it will mix with the old fuel as milk does in coffee.
Some armchair experts will offer advice to as to petrol being on the top or bottom but that is just guess work and not advice worth ruining your car over
Just had a call from a lady who had put petrol in a diesel honda earlyer today, she phoned the honda dealership and they collected the car with a low loader. (after she had driven it for 10 minutes)
After having the car sitting in the garage for a few days she had a call informing her that it was going to cost 4 thousand pounds to fix.
She got her breath back she started surfing the net for more information and found our site, she then called honda uk and told them what had happend and that the dealer wanted 4k for a rebuild, Honda told her to go ahead with a £180 fuel drain from us and go on holiday with the change.
Its good to hear that not all manufacturers are skinning the customers.
update; the job was done and started fine as per usual and she drove home from the garage in it – another happy cusomer
What do I do after putting wrong fuel in my car?
Is Petrol bad for a diesel engine? does it affect the common rail? drove a few miles with wrong fuel?
We get asked these questions all the time, and if you have been searching the net you would have noticed that there are quite a few opinions out there regarding wrong fuel and its consequences.
Putting petrol in a diesel car is easily done, and done much more often than people realise, we are one of many small independent businesses specialising in fuel drains, as well as the RAC AA and independent garages who do at least one a week,
If you have misfueld you have a few choices
1) “top up” with the right fuel and hope to dilute wrong fuel enough for engine to start, – NOT RECOMMENDED
2) call AA or RAC, they will either take you to a garage or drain it on the forecourt if they have availability, or most likely tow your car home and have one of their draining vans attend your house the next day, – cost 250+ and often a long wait
3) call the main dealer, (often done with newer cars), Main dealers have a bad habit of insisting a car needs new high pressure diesel pumps, injectors, fuel tank, fuel lines etc, often quoting £4000 to £7000 pounds, the party line is that petrol destroys parts of the engine and if the car has had petrol in it then certain things need replaced, this only goes on in the UK, the Germans dont tolerate being ripped off and if you misfuel a BMW or Mercedes in Germany and take it to a main dealer – they will do a simple fuel drain and not bother with rolling you or your insurance company over for a big pay out for un-needed work, the british main dealer for some reason holds a svengali like control of the average motorist, what I have observed is garages who know and have a good relationship with clients charge many times less than the norm for fuel drain repair work.
4) call a mobile fuel draining company, most petrol stations will have a card or 2 behind the counter of companies that can drain the fuel, this is done by inserting a special nozzle into the tank and sucking out the wrong fuel, and sometimes by connecting onto the fuel system internally and drawing it out of the feed end, the wrong fuel gets taken away in the van and the process takes half an hour to an hour depending on how much fuel is involved. they can normally arrive within the hour.
5) do it yourself, not recommended unless you are mechanically minded but for instructions have a look at our FAQs page
6) leave the car on the forecourt with the keys in it and go to india to find yourself
Sometimes owners of new cars misfuel heres one we done recently.
This car is less than a week old, on its very first visit to a petrol station in north London it was misfuelld.
The owner calld us and someone helped them to push it into a corner of the petrol station, we arrived 45 minutes later and performed a fuel drain.
The car was fine and hadent been started and once all the wrong fuel was removed we lifted the back seats and took out every last drop from the tank itself by accessing both access panels from the inside, we took extreme care whilst doing it to avoid ruining the new car smell with “eue de misfuel”
The car started perfectly after we brimmed it with the right fuel.
As a point of note; if a fuel drain is not done correctly a dealer can often tell if petrol is left in a diesel car by a number of things, the telltale “pfffft” as you open the diesel cap and petrol vapour escapes from the sealed pressurized tank, (diesel does not vapourize and expand like petrol)
The other way is sometimes the glue in the fuelfilter innards gets loosend by a throput of petrol, this does not happen in all cases and wont happen if a car has not been started with the wrong fuel
I do about 4 fuel drains a week from vauxhall cars (and vans) that have had the wrong fuel in them. Vuaxhall is making some good diesel cars lately, and not surprisingly some of them are getting the wrong fuel put in them. If you have put the wrong fuel or petrol in your diesel vuaxhall then don’t panic, they are easy to fix and don’t pose a challange to a competent fuel drainer. Vuaxhalls are front wheel drive mostly which means the fuel tank is a single unit instead of a twin fuel tank set up as seen in rear wheel drive cars. The easy way to remove wrong fuel from a Vauxhall is through the tank with a special fuel draining hose, however if the car has been driven then it will need to have a fuel system flush which is done by unclipping the feed line into the high pressure pump and drawing clean fuel through which purges the contaminated fuel out of the line. When a fuel purge is done it only draws clean fuel up to the high pressure pump, from the high pressure pump forward the contaminate (about 300ml) will have to be pushed through by the working of the pump and engine. Wrong fuel in a vuaxhall van is common, they also have a snag on the filler neck on newer vans which makes pulling the syphon hose out awkward, i have never looked into one so I dont know if it is an anti syphon device or just a sharp bend on the filler neck into the tank but you will have to be patient if you are drawing the syphon line out becuase it can catch and snag. vuaxhalls can be hard to start (impossible actually) if they have been driven with the wrong fuel and NOT had a fuel flush, there is about 1 litre of fuel that sits in the hoses, filters and pumps to the engine and if the fuel is not purged from the system it takes too long to purge it by simply turning the engine, trying to repeatedly start the car by turning the engine will flatten the battery at best and burn out the starter at worst, if you have put the wrong fuel in your vuaxhall car or van then I strongly suggest getting a fuel drain done by a professional
Over the weekend we had a callout from a lady in London who had misfuelled her brand new volkswagon scirroco TDi on saturday morning while putting the wrong fuel in at a BP station, she was a member of the AA and thought that it would be coverd by her membership and was then told it was 250 pounds and they could not attend her until sunday but they could tow her home and do it there, she then called volkswagon who told her she had to get it recoverd to a dealers, 10 minutes later the dealer called her qouting well into 4 figures but re-assuring her the car was coverd by her insurance and the costly engine re-build would not cost her anything. volkswagon sent out a recovery unit to bring the car in and she got a taxi home.
Checking with her insurance company she was told she was in fact not insured for misfuelling and the 4 figure sum was going to come out of her own pocket, she started googling the subject and found us, she called me this morning at 8am.
I met her at the dealership that it was sitting at and informed them that the car was to be released to me, 20 minutes later I completed the fuel drain, flushed the fuel system and re-filld it with clean fuel, it started first time and she drove off to work, to give the dealership credit they didnt try the usual scare stories or make threats of an invalid warranty and I got the impression they felt just a little bit guilty for trying to pull a fast one.
We do lots of fuel drains at car dealerships whereby the car has been towed in for extensive and un-needed repairs, in this instance the car had not even been started so an engine re-build was far fetched, even if the car had been started with the wrong fuel it would not have needed an expensive repair, a fuel drain and flush is a straightforward and non invasive procedure, think of it like keyhole surgery for a car.
If you have had a car taken to a dealership to have the wrong fuel removed you should consider getting a fuel drain first, its allot cheaper and can be done anywhere by a professional fuel draining company
Wrong fuel in a mercedes is something I am called out to frequently.
I Have done hundreds of Mercedes, including, a class wrong fuel , b class wrong fuel , e class wrong fuel, s class wrong fuel, petrol in diesel Mercedes vans is also a common problem, sprinters, vitos and even atego’s and some of the bigger trucks
If you’ve done it, dont panic, heres some simple pointers
Most mercedes are rear wheel drive – this means a twin tank system, not unlike BMW’s, you have a few options for getting the wrong fuel out of a merc.
1) call a fuel mechanic, they come to you and do the messy bit, it takes about an hour and costs between 160 to 200 quid.
2) pull up the back seat and reveal the 2 fuel tank access panels, unscrew the tops and then unscrew the big metal donut that holds the intank pump in, this is not a hand tight item, it needs a firm wack in the right place to unscrew it, once you unscrew that, unclip the fuel lines and electric plugs and remove it (the in tank pump and sender float) – this is the part where you cover the inside of your lovely car if “Eau de diesel”you are not carefull – dont worry it goes away in about 6 months, and if you stain the leather just wipe it all down with a diesely rag to make it blend in….. ok enough sarcasm. once you have access to the fuel simply syphon it out and refuel
3) open up the engine bay and find the flow line into the pump, south of the filter, disconnect it (you may need to remove the engine cowling depending on what type of merc it is) - the interception point is the most southernly accessible point on the fuel line, connect another hose to the fuel hose you have unplugged and put it into a container (25 litre drums work best) then simply put the key in the ignition and put it into accessory position which will send a cup of diesel thru each time, do this a few hundred times and you will have emptied the tank, then put in clean diesel and repeat the process, sending thru 2 litres of clean diesel to flush the lines, reconnect the lines and you are ready to go!
4) invest 25k in a fuel draining kit and simply pump it out into a tank in the back of your van, jack up the car at the side opposite the tank to transfer the fuel from the far tank to the near tank
There should not be any long lasting effects of misfuelling mercedes engines, although a freind of mine who works in a merc dealer sais he suspects that misfuelling does shorten injector life.
We attend many BMW’s that have been misfueld, mostly 5 series, the 5 series has a complicated fuel tank set up, in that it uses a “saddle bag” design, which is the tank hangs over the propshaft, which makes it 2 tanks joined by a pipe at the top, and elaborate pumping system to keep the levels equal, this dual fuel tank system with pumps to distribute fuel evenly was pioneered by concorde in the 60′s, because the engines burned fuel so fast, gravity alone would not keep fuel tanks equalised , bmw, audi, landrover, mercedes are among the cars that are using it, the reason is to cram awkward shape fuel tanks around prop shafts, exhausts, etc
Draining the fuel from a BMW involves more than emptying the tank with a suction kit, there will still be half the fuel left in the other side of the tank, to get to this you either have to bypass the cars internal “brain” and turn on the transfer pump, or you have to lift out the backseat and access both parts of the tank from above.
BMW’s sometimes signal a fault code after a misfuelling, this is normal and is the engine management computer is simply saying “engine dont work” which you already know by the time it comes on. this is not usually an indicator that something has gone terribly wrong, nor has it detected wrong fuel as the cause of the problem, once the car has been drained and filled with the right fuel and restarted, the engine management light will go out.
No permanent harm is caused by a brief misfuelling, so don’t get taken for a ride by a dealer who suggests a multi thousand pound engine and fuel pump rebuild, its just a scam that is peculiar to the UK, BMW main dealers in Germany simply recommend a fuel drain and wouldn’t dare try and pull the new engine/fuel pump trick that our dealers have been doing.
Call us if you need help with wrong fuel, a fuel drain, or advice on how to do one.
Recently, at Fuelfixer we have had quite a few call outs for ‘suspected misfuels’, i.e the car has broken down or is portraying symptoms of a misfuel, but the customer can’t remember if they have put the wrong fuel in. Or they have had a friend borrow their car and think that they might have put the wrong fuel in. And a lot of the time, the customer is right, it is a misfuel.
Now, it isn’t always a misfuel, but we are always happy to give advice and help you as best possible. If your car has symptoms of misfuel; it won’t accelerate no matter how much gas you give it, it has jerky and lerching movements, misfiring, or all together just brakes down and won’t start up again, there is a good chance you have put the wrong fuel in it.
Five times in the past two weeks I have been called to different suspected misfuellings, 4 of which were a case of wrong fuel and all i had those customers up and running again as quickly as possible.
I always try to do my best to get a car up and running again, and when its the customer isn’t sure if its a matter of the wrong fuel, i’m always happy to do my best to point you in the right direction if it isn’t.
There is nothing worse that not knowing what is wrong with your car, hopefully the symptoms above will help you figure it out. If you suspect the wrong fuel is in your car, call us, there is a good chance you are right!
There is always the nasal test, open your fuel cap and have a sniff, its not pleasant or healthy and (more than 2 sniffs is considered self medicating), diesel should smell like diesel, its got a duller oily smell, petrol is much stronger and sharper because it vaporizes constantly, if your diesel “smells a bit like petrol” then chances are it is petrol, if your still unsure sniff a diesel cars filler cap first for comparison.
Have you put PETROL in a DIESEL car?
(Or diesel in a petrol car?)
Call FUELFIXER NOW
Free from Landlines: 0800 015 9564
Free from Mobiles: 0345 073 9672
30 minute response time nationwide
1) We come to you, drain the tank and flush the fuel filters and pumps with clean fuel
2) Your car is not ruined, it does not need to sit in a garage for a week, nor does it need to be towed away or have expensive specialist work
ALL MAJOR CREDIT/DEBIT CARDS ACCEPTED
Even if the car has been driven we can rectify the problem and do a full draindown and flush – in 99% of cases this will have your car running normally again straight away.
We come to you. We are fully mobile and carry all the kit needed. We have professional fuel evacuation equipment on board and are experienced in all makes of cars & vans.
We supply you with fresh fuel at pump prices, and we can normally have your car done and ready to go in under an hour.
All waste fuel is disposed of by us through a licensed waste carrier and recycled.
Please read our guide to Misfuelling a diesel or petrol car. If you have been scared witless by stories of doom regarding putting the wrong fuel in, its not as bad as some say!
I see this sort of thing all the time, occasionally I take pictures, have a look at this below.
just another pump island… now look at this one
these are 2 islands in the same station, right next to each other, my customer was filling at one of them, his van was tight against the pump and he couldnt see his own pump island very well, so he looked at the one that was next to him and “drew his pistol” , this is where it went wrong.
The diesel on the top pump is on the right of the pump island
the diesel on the second pump is in the middle of the pump island
on the top island, both petrol pumps have green hose endings on the nozzles, the diesel pump has a black hose end
on the bottom pump the high octane pump on the right – petrol (which is where the diesel is on the top pump) – has a black hose ending
The high octane pumps colour flash, is grey, but it could also be faded black.
I took these pictures to send to the employer of the man who called me, he worked for a small transport company and was driving a brand new van (less than 1200 miles), that was the new pride of the fleet, he was genuinely worried that he might be laid off for what he had done, and opted to pay for it out of his own pocket to appease his transport manager, needless to say the wrong fuel was taken out and the fuel drainage was complete in 30 mins and he was on his way, I e-mailed these pictures to his transport manager and also pointed it out to the station owner.
The adverts on nozzles are a whole subject unto themselves, volkswagon ran a campaign recently on petrol pumps and in the text of the ad it said “diesel” this was on petrol pumps!
to prevent misfuelling; you cannot rely on old rules of thumb with hose colours, pump placements or even nozzle colours, now that every pump has an advert on it and every petrol station has branded fuel (excellium/premium/momentum etc) you have to be very carefull, it might seem a tad twee but if you follow these simple instructions, you should never suffer from misfuelling, if you need a fuel drain contact us
1) read the fuel type on your car/vans filler neck flap
2) look at all the nozzles and find the one that read ”Diesel”, – or petrol if your driving petrol
3) check to see that THE SPOUT END OF THE DIESEL PISTOL HOSE IS LARGER THAN THE SPOUT ENDS OF THE PETROL PETROL PISTOL. THIS IS THE ONLY FAILSAFE method, or if you are driving a petrol make sure it is smaller than the diesel.
4) if you do this, you will never misfuel, and if you do it will only be because some joker has changed the actual pump handles over.
if you have put the wrong fuel in your car and need a fuel drain becuase you have unleaded in your diesel car or petrol in your diesel tank, then feel free to call us, we are here 24 hours a day 7 days a week on 07514409700
So here is a list of the questions I get asked on or before nearly every job!.
Question; I drove my diesel car for 2 miles on petrol after I filled it up then it just died on me, will it need repaired
Answer; you didnt drive it for 2 miles on petrol, what more likely is you drove it for 2 miles with petrol in the tank, once the petrol made its way through the low pressure sender pump, thru all the fuel lines, up to and through the filter (holds about a pint of fuel), through the hoses to the high pressure pump, thru the pump, into the common rail resovoir, and finally into the high pressure lines into the combustion chamber, that’s normally the exact point that the engine stops turning, and in fact you will find you maybe got about 20 yards on petrol, which is the time it took for the engine to stall. the good news is, this isn’t as catastrophic as you might think and there is a simple, effective solution in a mobile fuel drain – a service we provide all over the country and we attend most call outs with 50 minutes, 24 hours a day. there are many different things that can happen with misfuelling, I have covered most of them below .
This is a typical case of a car that was driven for about 20 miles on the wrong fuel. We got the call out when the owner couldn’t start it in the morning, and then realised she had misfueled it the day before. This car had been drained from the tank and the fuel system flushed through, if you listen in the beginning the sound may be familiar to anybody who has tried to start a misfuelled car. But as the car starts, it quickly goes back to sounding normal. 99% of breakdowns caused by misfuel are this easy to fix. Humble apologies for the quality of this video, I took it on my phone, because it was the camera man’s day off!
Question; what does petrol do to a diesel car’s fuel system?
This picture (above) is the suction line I use to remove wrong fuel . this was taken when doing a job that had 50 litres of petrol in a diesel mini, this was being taken from the fuel tank as the car had not been started. this hose is full of fuel, about 70% petrol, 30% diesel
This is a picture of the same hose, the car was a Diesel VW Polo, it has been fill’d with 90% petrol, and 10% diesel, the car had been left overnight after loosing power and being towed back to the customers house, the suction line was attached to the high pressure pump inlet, as you can see the fuel has gone black, this is becuase the petrol has desolved rubber in the fuel lines, this car sat for a day with a very strong mix of petrol, it had also been driven until failure, the dark colour is a mix of rubber and plastic that has dissolved in petrol (fuel hoses are made type specific to reduce costs for car manufacturers,i,e diesel for diesel hoses only and petrol in petrol hoses only), I would not expect this to have done the car any real harm over an 18 hour period, just a microscopic layer of fuel line has been stripped off from the inside, these lines are fairly thick so a short bit of contamination once is fine, if you do want to make a habit of misfuelling regularly and leaving the car sitting for days with the wrong fuel in it you will eventually need new fuel lines. and plastic fuel components
Question; what happens to the fuel once we take it out?
Answer; at the end of the day (or during a very busy day), I unload all of my mixed fuel into 220 litres drums, at our garage, (a licence is required to store mixed fuel from the enviroment agency), the mix is collected every 7 to 10 days by a garage services company, these are the same guys who take away used engine oil, brake fluid etc.. from garages everywhere. the mixed fuel is batched seperetly and in-between me and all the other companys that offer this service, I would guess that there is between 50 to 200 thousand litres a week of mixed fuel “made” in the UK per week. – once it is batched up into viable quantities usually 28.000 litres (tanker load) it is refined in one of the main refinery’s using a distillation process – identical to the one used for making crude oil, the petrol diesel mix seperates at 60 – celsius, i,e the petrol fumes off, it is then condensed and seperated, from what I have heard this is done twice to get a proper result, I would assume that the mix would then go back into the supply chain and be used as it was originally intended!
Question; I put the wrong fuel in – have I damaged my car?
Answer; it is very unlikely that you have, pretty much 1 for 1 call outs I attend are back up and running again when drained, if you have not started your car, you will not have damaged it. if you have driven your car and it stalled, or would not re-start then the chances of any lasting damage are very slim, there’s a bit of a safety mechanism that works by defualt and it goes like ”petrol will ruin your diesel car but your diesel car will not run on petrol long enough to get ruined, therefore, PETROL WILL NOT RUIN YOUR DIESEL CAR”
Question; my car conked out, have I wrecked it?
Answer; no, as above “conking out” is your engines way of saying “I am not moving untill you get the wrong fuel out of me and the right fuel in”, I attend many “conk outs” “died” “made horrible noises” etc.. once they have been drained down , 20 litres of correct fuel put in -and the system fully purged upto the high pressure pump fuel inlet – then , they all ran fine afterwards
Question; my car has a common rail pump, are you sure its going to be fine?
Answer; YES!, the vast majority of new diesel cars have sophisticated common rail pumps, we attend them day in, day out what I have written above applies specifically to common rails
Question; whats worse, diesel in petrol, or petrol in diesel?
Answer; the wrong fuel in varying quantities does different things, petrol in diesel will stall it, or depending on the mixture it might just still run, albeit sounding like a bag of spanners, – with reduced power Diesel in a petrol car will make it lose power, and run flat. The worst case scenarios (and these are the WORST) are;
1) petrol in a diesel pump will eventually damage the pump (If you are unlucky enough to get a mix that just runs) , if you have not noticed it, and are completely oblivious to the car’s behaviour, you would also have to do a fair ammount of driving with a heavy foot, this would require a new common rail pump, piezo injectors and fuel lines, the high pressure fuel pump which operates at 28 oddd thousand PSI of pressure and is a highley enginerd unit relies on diesel going thru it to provide lubrication, petrol does not lubricate, in fact it has “anti lubricating” properties, hence why petrol is good for cleaning out oil stains. what happens is the inner working of the high pressure pump start chaffing metal grinds on metal, this destroys the pump, then the metal chafe gets drawn thru to the piezo injectors and ruins them as well, now before you go and sell a kidney to pay for a new diesel pump and injectors, please read the read the rest of these FAQ’s because full scale damage like this is very very rare.
2) diesel in petrol worst case scenario, the diesel will enter the cylinder and not burn, it will slide past the piston rings, into the oil sump and therefore the cars oil system, this will increase the oil level, to a point that could cause total engine failure, i.e mangled rods, bent pistons, complete block failure, or the thining of the oil can reduce lubrication to the engine and it could suffer from a full seizure/big end failure/ruined propshaft. Again this would not be an easy thing to do, the car would be very low on power and not running right, you would have to do a good bit of driving in it to achieve the above.
Question; land rover/mercedes/bmw/audi etc all insist I bring it into the garage for a full drain and it will cost ££££££££££ what should I do?
Answer: main dealers and “tooth sucking garages” will sometimes take a misfuel case for all its worth. I have heard of people having misfueled cars collected by main dealers (these cars had not be started and were collected from the petrol station forecourt) and then the insurance company picks up a tab for 5 or 6 thousand pounds for parts that absoloutley dont need replaced, (and I would suspect never get replaced), this is all very well untill you lose your no claims bonus and when you trade your car in eventually you have to explain why it had so much major work when it was brand new,
Question; but the maindealer says I must bring it in otherwise the engine and pump will be ruined,
Answer; I’ve got a fair bit to say about this, probably the most high profile example of manufacturers being totally inflexible was the Icelandic volcano eruption , and the disruption to flights, it went like this, there was a small amount of ash detected in the air space, as a precuation the authorities asked Boeing & Rolls Royce what was a “safe” and what was an “unsafe” amount of ash for jet engines to fly in, the responce they got was “zero”, therefore all flying was banned. because none of the big engine makers would go out on a limb and come up with a “safe” level of ash everything came to a stop – (until the airlines started flying empty planes round in circles to prove that it was actually safe) Coming back to the automotive industry, the car manufacturers have a similar one policy fits all approach to wrong fuel in cars, , and that is certain things must get replaced after a fuel drain regardless of how much fuel was put in, for how long, or whether the car was driven. They win both ways, firstly they sell lots of parts and millions of hours of labour that wouldn’t otherwise be sold – and secondly they never have to deal with someone claiming warranty if there is any possibility of wrong fuel being used , they know that petrol in small temporary quantities won’t destroy a diesel engine, but they could never say it, because it they are wrong on just one car once… its would be one too many, that’s the manufacturers approach, and the main dealer network quickly caught up with the idea of turning it into a lucrative money spinner and starting milking customers and insurance companies for thousands of pounds.
Question; I’ve read everything here but the stuff I read on the net and in car forums says otherwise, I still don’t know what to do?
Answer; I don’t blame you, I have seen the various discussions in forums on the net – it makes for scary reading if you have put petrol in a diesel car, you will find most of them are repeating threads from older posts, who have re-hashed threads from even older posts, that were written by armchair mechanics , the amount of conflicting information is also a clue as to the validity of the content, there’s a lot of people talking a lot about something they know very little about, I do fuel drains, its my livelyhood, I do dozens every week, I have attended thousands of call outs, I have seen customers who I did fuel drains on after they had driven 10.0o0 20.000 and even 50.000 miles in their cars after putting the wrong fuel in and being drained, none of them had any damage that developed after the misfuel,
Question; I’m in a hire car, should I call them and have them arrange something,
Answer. (I dont mind getting a legal letter on this one becuase I know it to be true)
I received a call from a man in Canada on Tuesday, last week he was in the UK and misfuelld in a HERTZ rental car, the forecourt attendant gave him my card, before he called me he had a quick look at the rental agreement, it was quite clear that he was obliged to tell Hertz what had happened, so he did, and they sent the AA. his card was then debited for £500 odd pounds, now the AA charge between £100 if they are quiet, to £230 if they are busy for a misfuel (no it is not covered by AA membership), so how did he end up paying £500?, Hertz called the AA and I assume got a whacking corporate discount and had the job done for 50 or 60 quid, they then put the boot in and charged the customer £500, he didnt have a choice in the matter because they had his card details, so if you are in a hire car you could either, call an independent mobile fuel drain company, or if that makes you uneasy – call the AA yourself , and pay for it yourself, you will save a small fortune.
Question; I have read all the above, now I think I will top up with the right fuel and chance my luck will that be ok?
Answer; hmm… I would always recommend a full fuel drain, not because I want your business but because petrol does not do any good in diesel engines, it can corrode rubber hoses and plastic seals that are fuel type specific (petrol and diesel behave differently on different materials, , so the car manufacturers use different plastics and rubber in the fuel system) , as much as I believe wrong fuel will not wreck a car, that is based upon the wrong fuel being taken out as soon as the mistake has been spotted, petrol in a diesel engine will eventually cause problems if not dealt with, but if you are driving an old knacker that will be scrapped when it fails its MOT that is due in a month then you might as well just risk it, but otherwise DRAIN DRAIN DRAIN
QUESTION;can I keep the wrong fuel after you drain it, I want to use it in my lawnmower
Answer. there are easier ways of getting out of mowing the lawn other than ruining your lawn mower with a petrol diesel mix, maybe you should feign injury or concrete over the garden. Really misfuel is not worth trying to use, even if you think you have just put 80 quid of petrol in your range rover sport and assume you have a 99% petrol mix, allow me to elaborate.
when you drive a car your fuel sloshes around the tank, (even with baffles) when it gets low and sloshes too much it draws air into the fuel system, this is what running out of fuel feels like, however the tank is not totally empty at this point, it merely cannot supply a constant flow of fuel without interruption, but there is still around 5 to 10 litres in the tank, this changes the sums when you are calculating the “purity” of the mixed fuel, and you will actually have a fair bit more diesel in the mix than you thought you had, allot of people tell me that the “gauge said 3 miles left” and when Í’ve finished the drain and they fill back up they find they got 20 quid more in it that they ever had, and are genuinely surprises how big the tank actually is, that said, if you really feel attached to it and have suitable containers and somewhere safe to store it, then I might just let you keep it, I will expect coffee, biscuits and perhaps a sandwich or two for the privilege
Question; Are there a lot of idiots/wallies/Muppets who misfuel like me?
Answer; I have met some of the nicest people doing fuel drains, in fact it has restored my faith in humanity! You most likely are not a Muppet, fuel filling pumps are very unstandard and there is no uniform colour coding of pumps, the AA released a snippet a few years ago that 300.000 people per year misfuel, I think the true number is many times that, and the number of people who only misfuel by a pound or so is astonishing, people who lead busy lives or drive more than one car are more likely to misfuel, some older customers joke that maybe they have gone senile – and it doesn’t even occur to them that they have driven a petrol car for 40 years and just got a diesel fiesta because there son insisted they get a more economical car – (and were embarrassed about the 1985 Cortina that mum and dad were running around in), don’t beat yourself up, you most likely live a busy life and have responsibilities that take up a lot of your attention, misfuelling is not the beginning of dementia, nor is it indicative of a low IQ, anyone who gives you a hard time or carries the joke on too long, is probably the sort of person who has a go at everyone about everything, so don’t take it personally, one day it will happen to them too. The “at risk groups” are mothers with young children, (try filling up with toddlers), anyone in a rush, fleet drivers who run a petrol home car and diesel work car, and of course Muppets joke;-)
Question; does the petrol seperate and float on top of diesel or does the diesel float on top of petrol?
Answer; neither, they blend instantly in the tank and it becomes a fairly even mixture, although they are different compounds, (technically speaking the carbon chain on diesel is longer) , they both come from crude oil, petrol and diesel spend millions of years in the ground as one and the same as part of crude, only refining seperates them, and once recombined they will mix together and stay together untill refined.
Question; I have heard of petrol being used as an additive in diesel in colder climates, why
Answer, yes, it can be used as an ad-hoc winter fuel additive, in remote freezing areas that do not have a well established supply chain of fuel, (think Arctic weather stations), in the UK however we have a very good supply chain of fuel and winter additive is added by the refiners as early as September, the engines that can tolerate a bit of petrol are lower technology diesels, that do not have the high pressure pumps that are found in the cars of today, I would not recommend using Petrol as an additive to diesel, I heard from a skip hire company in edinburgh that used to add petrol into diesel – but they stopped doing it in the 90′s
My engine management light has come on – what does that mean
Engine management lights come on for a number of different reasons, on Volkswagons for example when they have been driven on the wrong fuel and drained, they often take a while to restart sometime 3 bursts of 30 seconds cranking, it is not un-common for the low oil light to come on when it first fires up, it goes off after a minute or 2, engine management computers are not very informative, they either say – “no problem” or “problem”, petrol in a diesel car will confuse sophisticated engine management computers, they are designed to regulate air and fuel flow, air pressure, exhaust pressure, exhausttemperature, ignition timing, all to give optimum performance, economy and emissions, when you put petrol in the tank it throws all the calculations off, some very intelligent engine management units cars will even try to “adjust” to the contaminated fuel, and when they fail as they always do, they will sometimes read a fault, the vast majority of fault codes generated by a wrong fuel scenario are temporary, which means once a fuel drain has been performed – the engine will detect that the conditions that caused the problem are no longer present – thus assumes the problem is solved and the EM light will go out, It is very rare that a light stays on after a fuel drain and restart, this is one of the reasons why I would always suggest a professional drain on a new car, a professional drain will remove as much fuel as is possible, which mitigates possible damage
I put the wrong fuel in, do I need a new fuel filter.
No you not need a new filter.
This idea came about from the “logical” assumption that the filter would be contaminated with condensed amounts of wrong fuel and thus continue to weep wrong fuel into the system, a filter does not hold much fuel – and petrol and diesel certainly do not “condense” 300 to 400 ml of fluid is what a filter holds, the filter is simply a housing, with a cardboard, paper type filament to catch solid debris, a diesel filter has 2 purposes, to prevent water from getting into the engine via a water trap – which needs emptied on servicing or by dashboard warning light sensor, and to stop solid debris from the tank from getting into the engine, diesel and petrol are neither, and petrol does not “sit” in a fuel filter, likewise when diesel is put in a petrol car it does not sit in the system when a fuel drain is performed of a car that has been driven to failure on wrong fuel a flush is done of the filter, this involves pumping the correct fuel through the filter, which purges the filter completely, after a proper fuel drain a filter will be clear of the wrong fuel, I think that this is sometimes used as an excuse by some garages to inflate the price of a fuel drain, the truth is that most fuel filters cost a whopping 4 pounds, and take a lenghty 6 to 8 minutes to change, I have seen garages charge over 150 pounds for a filter change, and If I was morally bankrupt I would be getting in on it to, but the truth is that there no reason to change a filter unless it is due per the service book, that said some people still want filters changed during a fuel drain for peace of mind, which I have done occasionally if the filter is supplied, for the princely sum of a cup of tea and a heap of biscuits, (chocolate).
a very good article on this subject was written by auto express, here is the link here
This was re-hashed by the daily mail here