# How many miles could you drive a diesel car with petrol before noticing?

I recently refuelled my brand new diesel engine car when it was basically empty (25 miles left) and then drove away. I drove the car for about 100 miles before noticing the standard juddering that you get with some kind of contaminated fuel.

I am like 99.99% percent sure that I put diesel in the car but let's assume that I actually put petrol in. Is it possible that I could drive 100 miles in a diesel car on petrol (with a small amount of diesel remaining) without noticing? If this is possible then how likely is it?

• Whatever you do: Keep the receipt of the fuel station Nov 26, 2020 at 16:01
• "Is it possible that I could drive 100 miles in a diesel car on petrol (with a small amount of diesel remaining) without noticing?" Apparently you did notice something. We can not provide and answer to that. "If this is possible then how likely is it?" It seems like it is could be likely since you think you did it. Shouldn't your question be "How much if any damage would be done to a diesel engine if i accidentally drove it with gasoline in the tank?" "I am like 99.99% percent sure" like 99.99% sure or actually 99.99% sure? Nov 26, 2020 at 19:59
• If you are unsure: dip the tank(with a polythene tube). If you only had about half a gallon of diesel left, then it should be obvious whether it is diesel or mostly petrol. Nov 26, 2020 at 22:32

New diesels run very badly on gasoline, if you filled up the tank with gasoline you'd know very quickly as the fuels do mix. Your engine would run rough, spew out lots of black smoke and have poor performance and mileage. If it took 100 miles to notice a judder it's very unlikely to be from contaminated fuel.

If it's a modern tight tolerance VW engine or such you won't get far. The fuel injection system will wear itself out and make metal fragments in the first 30 miles. The older 80s diesels like the Mercedes can go through a tank or more before damage is noticed. It would heavily depend on how much diesel oil is mixed with the gasoline.

You can buy lubrication enhancing fuel additives for diesel that might also work in gasoline that would reduce the damage from gasoline in a fuel system that is meant for fuel oil.