What happens if you put oil in a car's gas tank?

If a little oil is poured into the gas tank of a car, it burns up in the engine cylinders, causing the car to produce blue smoke and run roughly until the oil is gone. In the vast majority of cases, this does not cause permanent damage to the vehicle.

If oil has accidentally been added to the gas tank of a vehicle, it can be diluted with gasoline to mitigate the effects of the oil on the engine. If the gas tank is completely full of oil, it may be necessary to drain it before adding fresh gasoline, but cleaning the oil out of the fuel line is not required.