What happens if you fill a diesel car with petrol

A diesel fuel pump operates on very fine tolerance at high pressures and is lubricated by diesel fuel. When petrol is added to diesel it reduces its lubrication properties, which can damage the fuel pump through metal-to-metal contact and create metal particles causing significant damage to the rest of the fuel system. Serious engine damage may occur due to detonation caused by uncontrolled petrol ignition under the much higher compression ratio in diesel engines, also known as pre-ignition, detonation or misfire.

The best-case scenario will involve a call to NRMA roadside assistance and a tow to a mechanic to drain the tank, fit new filters, and refill the tank. If you try to drive the vehicle, however, it could result in several thousand dollars of repairs to its fuel system and time off the road. If you started your car and drove away before you realised your mistake, stop somewhere safe as soon as you can and switch the engine off to minimise damage.

However, driving a diesel car with petrol in the tank will cause serious and expensive damage in fairly short order, and the potential cost of extensive repair is not worth the gamble. Even if you get away with running the engine or driving without damage, the incident will still be more expensive. Now read about the Most economical SUVs, 4x4s and crossovers Skip to Content Skip to Footer.

If you do want to risk driving on, stop frequently to top up the diesel and thus reduce the percentage of petrol in your tank as quickly as possible. Inform the filling station attendants: They will take it in their stride, as it happens to hapless motorists all the time. If they want you to move your car, ask them to help you push it — remembering to turn the key in the ignition just far enough to unlock the steering.

Call your breakdown service or a specialist misfuelling service: The filling station will likely have contact details for a suitable company if your breakdown service can't assist. Don't be harassed into using an operator you're not comfortable with though, as you can find well-known nationwide operators using google and a smartphone. You should contact a wrong fuel recovery service who will conduct a fuel drain and flush. Diesel fuel pumps operate on very fine tolerance at high pressures and are lubricated by the diesel fuel.

When petrol is added to diesel fuel, the mix acts as a solvent, reducing lubrication. This can also cause damage to the fuel pump through metal-to-metal contact creating metal particles, which can cause significant damage to the rest of the fuel system. Serious engine damage may also occur due to detonation knocking caused by uncontrolled petrol ignition under a much higher compression pressure consistent with the diesel engine.

The further the petrol moves along your fuel system, the increased potential for a more expensive the repair bill. Our biggest word of advice is to always double check the fuel grade indicator on the pump before filling up.

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