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.