What to do if you’ve put gasoline in your diesel.

Note:  Normally gasoline will ruin a diesel High Pressure Fuel Pump (HPFP).

Models effected: All year models of OM612, OM642, OM647 and OM651 diesel engines.

The following procedure should be followed when the above model diesel powered vehicles with a common rail injection system have been refueled with an incorrect fuel type such as gasoline, kerosene, water, biodiesel, AdBlue/DEF, and/or other mixtures thereof.  In addition, biodiesel fuel above 5% (B5) in the fuel tank is not permitted for use in the above model vehicles. Please follow the procedure below.
If the fuel tank is filled with the wrong type of fuel this will not be submitted as a warranty claim. Even if you didn’t use the wrong fuel and Mercedes finds metal shavings in the fuel system, they will still not warranty the fuel system.  A smart owner would make sure to have a rider on your insurance policy that covered you for any fuel system failures that are blamed on the fuel. Mercedes typically wants $15,000 to $20,000 to replace a BlueTec fuel system.

If the engine was NOT started after the fuel tank was filled with the wrong type of fuel, then emptying the tank and cleaning the fuel low-pressure lines should be enough to resolve the problem.
If the engine was started after the fuel tank was filled with the wrong type of fuel, disconnect the Y- distributor unit (return line high pressure pump/rail) at the output and with the ignition ON collect the fuel in a clean container.  Check fuel for shavings.  If you see metal shavings, you will not be able to save the system.

If there are no shavings in the injection system and the high pressure pump is not damaged, emptying the fuel tank, cleaning the low pressure lines and changing the fuel filter should resolve the condition.
If metal shavings are found in the injection system and/or the high pressure pump is damaged, replace the following components to ensure there are no metal particles in the fuel system.  Refer to Mercedes Benz for the applicable part number for the engine model affected.
• Fuel Tank
• Low Pressure fuel pump
• Fuel Filter
• High Pressure pump
• Rail (Including Pressure regulating valve and the rail pressure sensor)
• High pressure lines and the leak lines
• Injectors
The low pressure lines need to be thoroughly cleaned, at least twice or replaced.


Always add a quart of Marvel Mystery oil to every tank of fuel. There are many good fuel additives. You don’t have to use MMO. MMO has been around a long time and is well known to protect the fuel system. This will help mitigate the damage if you didn’t know the fuel was contaminated. Place high strength magnets on the bottom of the fuel tank and attach magnets to the fuel lines going to the filter and the High Pressure Fuel Pump (HPFP). You can order the magnets off of eBay. The magnets will prevent any stray metal shavings from damaging the fuel system.  There are to many reports of owners with metal shavings in the fuel system and no evidence of the wrong fuel being used.  Other German diesel automakers are having trouble with metal shavings coming from the Low Pressure delivery pump in the tank.  If you are 100% certain no bad fuel was used, remove the fuel pump in the tank and inspect for rust or other signs of corrosion.  If there are metal shavings and no signs of corrosion, the pump itself caused the metal shavings.

Change the engine oil every 5,000 miles. The HPFP is lubricated with the engine oil. If the oil breaks down, the HPFP can fail.
If you know you’ve pumped in no more than 5 gallons of gas, you can add a extra quart of MMO for each gallon of gas. Also add a bottle of Cetane diesel fuel additive. Then top off the tank with diesel fuel. Drive 50 miles and top off the tank again. Do that for the next 200 miles. This is when you are far from home and it’s hard to find any help. More than 5 gallons of gas, and the tank really should be drained. If it’s a dire emergency, add a quart of MMO for every gallon of gas up to no more than 10 gallons. Add 3 or 4 bottles of Cetane. Top off with diesel fuel as often as you can.

If you’ve driven the vehicle and it quits because you put gas in the tank, this will be much harder and may not work. This is only incase you are stranded and have no choice. Suck out as much fuel as you can and refill with diesel fuel. Add a gallon of MMO. Remove the fuel filter and fill with MMO. Crank the engine over for a couple of minutes. You’re trying to get the MMO into the HPFP and the injectors so they will free up. As you crank the engine, diesel fuel should start to fill the lines. Keep cranking and hope that it starts. This is a last ditch effort if you are no where close to help.