I put petrol in a diesel engine

I borrowed a friends 2003 Mercedes Vito and put about 10 liters of petrol in an empty tank. It drove for about a kilometer or two, than died out… No dramatic noise, just sputtered out. Wondering what the damage could be best and worst case scenario. Is it possible that the car just ran on deisel in the fuel lines, and than as soon as petrol entered it shut off? because the car does not start now, and it seems as if the gas pedal doesn’t really engage. If there was petrol it would still actually turn on, right? This tells me that there may be some auto cut off? Mechanic is telling me that the entire fuel injection and pump system is going to be ruined, but I have a hard time believing that this is a Garuntee… What’s your guys take on it?

I’m no expert, but my understanding is that gas (petrol) in a diesel engine will do expensive damage (unlike the other way around). I’m afraid you’re likely to owe your friend a lot of money here.

While I can’t guarantee it, I believe that lion9car is correct.
The OP needs to be honest with his friend about the scenario that took place, and he needs to cover the high cost of repairing his friend’s car.

I really was looking for somebody that knew what they were talking about to maybe chip in some advice.

You cannot run gasoline (petrol) thru the injector pump/diesel injectors without doing some kind of damage to the fuel system.

Drain the fuel tank, fill it with diesel fuel, cross your fingers and start the engine.


The mechanic is correct and maybe a prayer to the auto gods could help. Or not.

I would hope that a 2003 year model vehicle with unspecified miles did not suffer engine damage also. Diesels can be very cantankerous about compression issues and Benz repairs are not cheap.

Something else to consider is the closeness of this friendship. Any current problem or one that pops up in 6 months or a year may be laid at your feet.

The explanation below and more can be found here.

“…it all depends on how much diesel remained in the tank before the gasoline was added, and how new and sophisticated the diesel engine is. In a 2007 or newer clean diesel engine, any amount of gasoline will probably damage the sensitive emissions control components (DPF, OxyCat and SCR) and system. In older engines with much less sophisticated and “touchy” emissions systems, a lightly diluted (say 90 percent diesel/10 percent gasoline) mix would probably pass through with little or no detriment. It might simply cause reduced engine power, perhaps a bit more noise, and possibly a sharp warning from the emissions sensors that detect something other than pure diesel exhaust. It’s high concentrations of gasoline that spell real trouble.”

Condor08 wrote:
I really was looking for somebody that knew what they were talking about to maybe chip in some advice.

I’m sorry that you don’t like the quality of the advice you received (after only a half hour, I’ll note). We’ll make sure you get a full refund on the price you paid for this advice.

The specs show the fuel tank is 78 Liters.

The OP says they put 10 Liters in an empty fuel tank so I’d say what little diesel was in there was highly diluted.

Joe Guy: OP stated about 2.5 gallons in empty tank. It looks like another OP searching for good news and being disappointed when not getting it. I may have information but they have now been put on ignore as my news is not good.

I assume that since you refer to petrol instead of gas or gasoline that you are in England or Europe

You have several problems here.

One is that you have to drain the fuel system and hope it was not damaged by petrol.

Since you did not have any major noise you may have avoided engine damage. Diesel combusts by compression, petrol by a spark. Petrol can detonate (pre ignition or pinging) by compression that is too high. A diesel engine has much higher compression than petrol is designed for. If you are lucky the fuel system failed before petrol got to the engine and started massive pinging. If you are not lucky, the petrol got into the cylinders and started to pre ignite to the point that it damaged the connecting rods or crank shaft, which would have stopped the engine. The lack of major noise may be a good sign for you, the damage to these components can be very loud. But for whatever reason the engine stopped.

You also have a dilemma on what to do with the mixed fuel. It cannot be used in a diesel, it cannot be used in a petrol vehicle. Euro hazmat standards are somewhat more strict than the States, but no matter where you are you have to find an acceptable way to dispose of the mixed fuel.

Let your friend know what happened, get the car to the mechanic of his choice and hope for the best

All advice is worth at least the price paid.

Agree with Tester. Diesel is oily and lubricates the injector pump. Gas will not so worst case injector pump, injectors, and assorted parts. Best case you lucked out. Back in the 80’s more than one diesel Caddy or Olds was towed in for expensive repairs from putting gas in.

Find it hard to believe that a kilometer would have ruined it,but that gasoline preigniting would have been ,bamming the pistons pretty hard.Had an acquaintence who destroyed an Olds diesel,by trying to run a tank of gas through it,gas pretty much acts like ether in the combustion chamber of a diesel(you can actually start some old diesels on gas in the winter,the old Farmall MD tractors started on gas and switched to diesel,when they were warmed up)

The car will not restart, a diesel motor will not run on petrol (gasoline). The car ran until the diesel in the fuel lines was used up and when the petrol replaced the diesel fuel the car died.

Is there an auto shut off? I say no. An auto shut off means a sensor would have to know the difference between gas and diesel fuel and cut off power to the fuel pump. It could be done, but I’m not aware of any cars and trucks that have one. The car isn’t running because of the petrol.

The fuel petal feeling disengaged is just that a feeling. This car has a “drive by wire” set up, there is no mechanical linkage to the fuel petal. It is an electrical potentiometer on the petal and small motor at the throttle body and the two are connected via a wire.

The car will not run so it will need to be towed to a mechanic. A MB dealer knows the car best, but a good shop should be able to handle it.

What is the best case scenario? Remove all the petrol from the tank and add a few liters of diesel fuel. Disconnect the fuel line at the motor and run the fuel pump to remove all the petrol from the fuel lines. Change all the fuel filters (the petrol will degrade the filters). Reconnect the fuel line and see if the engine will start. If it does it will be rough for a short time, but should smooth out in a minute or so. If it runs but not smoothly go to worst case scenario.

The worst case is there is significant damage to the fuel pump, or fuel injectors, or fuel pressure regulators, some or all. Even worse would be damage to pistons and internal mechanical parts. The lack of major noise and knocking as the car died tells me that internal damage isn’t likely.

Petrol is a very different animal than diesel fuel. Petrol can eat away and degrade seals and parts that tolerate diesel fuel with no problems. That means the faster the petrol is cleared out of the system the better.

I really was looking for somebody that knew what they were talking about to maybe chip in some advice." - OP

I don’t think the OP is here anymore. He was looking for a cheap way out and didn’t get the answer he’d hoped for. :neutral:

I don’t think the OP is still here either but I have a feeling it’s going to be an expensive repair for { SOMEONE } even if it’s just draining , cleaning & flushing the entire fuel system .

I have drained gasoline from a half dozen or more diesel pick up trucks. Two hours labor and a fuel filter is the normal rate but these trucks still ran. If a diesel is driven to the point the high pressure injection pump fails it will cost $2,000 plus. Gasoline will not lubricate the injection pump and cause failure.

In the cases with the pick up trucks the operators generally refill at 1/4 tank, which is about 10 gallons remaining. Adding 20 gallons of gasoline to 10 gallons of diesel will still provide a small amount of lubrication. They usually realize something is wrong by the ignition noise and smoke.

In the US, years ago a special nozzle was developed and a smaller opening in the filler pipe was installed so that cars needing unleaded gas couldn’t be filled with leaded gas. The nozzle for leaded gas was bigger and won’t fit and if you tried you got soaked with gas.

It seems putting gas into a diesel car is a really easy mistake to make. As more cars in the US are diesel I guess this mistake will occur with greater frequency. Is there a fix?

Is there a fix?

It’s self-correcting…you’ll only do it once.


It WAS an easy mistake in the early '70s. However, as you yourself pointed out, fill holes for diesels too small to accept gasoline pump nozzles have made it an almost impossible mistake to make.