So you think you may have put diesel in your petrol car, what does this mean for your car? The good news is that putting diesel in a petrol engine should not cause any long term and expensive damage to your car, even if you have driven the car with a large amount of the wrong fuel in the tank. Putting diesel in a petrol car is not especially common because the diesel nozzle is generally bigger than the petrol nozzle.
The common signs of having your petrol contaminated with diesel is that the engine may start misfiring, it won’t want to start, the engine can cut out or you may have a smoky exhaust when driving. If you have any of these symptoms listed and think you may have put diesel in a petrol, STOP DRIVING when it is safe to do so and switch off your engine. This will avoid any further contamination to your engine with the diesel residue.
Unlike diesel, which has to be compressed to ignite, petrol is ignited by a spark generated by the spark plugs. If the car is started the diesel will clog up the spark plugs and fuel system, causing the vehicle to misfire, smoke and possibly stop running. After the contaminated fuel has been flushed from the system, the bike or car should start fairly quickly. You will initially see smoke whilst the diesel residue is burnt off, after this the vehicle should run as before the incident.
The good news is that putting diesel in a petrol is far less serious than if you were to put petrol in diesel. You are unlikely to have done any permanent damage to your engine or fuel system. A full flush of the fuel lines and tank is essential to remove any contaminated fuel. Once this flush has been carried out and the vehicle has cleared the remaining residue diesel from the system, your car should run fine. We do recommend, as an extra precaution, that you change your fuel filter within a few days of the incident, these are a relatively low cost component and are simple to install.