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Petrol in a Diesel Car

Putting petrol in a diesel car is a common mistake and in 99.9% of situations is able to be fixed. It appears to be the more common mistake than diesel in petrol cars. We would assume that this is because unfortunately the petrol nozzle is able to fit into the fuel filler neck.

Whilst putting petrol in a diesel car may be the result of being new to the vehicle or simply being distracted while filling up, knowing what to do in this situation is vital for your safety and can also save you thousands in repair bills.

Although the mistake is fixable, it should be known that there are some serious issues that can arise out of putting petrol into diesel vehicles.

First and foremost is your safety and the people around you. Petrol is extremely flammable, so we would encourage you to avoid handling. Secondly, the petrol has the potential to cause serious damage to the fuel injection system and the engine, the resultant damage is not covered under warranty and insurance policies may not provide cover for the mistake.

My partner made the silly mistake of putting petrol in our diesel car and within the hour, wrong fuel rescue was with us at 10pm at night and had us ready to go for the next Morning. For something that could have cost thousands, this was the best service I could have asked for! Thanks so much!
Cassie May, Perth WA, Facebook Reviews

What to do?

DO NOT START YOUR ENGINE or put your key in the ignition as this can prime the electric pump in the tank and circulate the wrong fuel. It is essential to carry out a full fuel drain. Once the wrong fuel has been removed and the tank filled with the correct fuel there should be no damage to the engine.

Already driven car before realising?

If you have already started your vehicle, STOP driving as soon as it is safe to do so.

In this situation, it is recommended to take every precaution to remove all of the incorrect fuel by a licensed professional. A full tank drain, and complete fuel system flush is essential to stop or minimise any potential damage from to your vehicle’s fuel system.

Once the system has been completely flushed through with the correct fuel and the tank has been filled with Diesel, a full diagnostic check of the engine management system will be carried out to ensure no damage to the engine has been caused.

What happens?

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. So, if you have already started driving, as soon as you realise you have contaminated your diesel with petrol STOP DRIVING and SWITCH OFF!

Reduce the risk

Our biggest word of advice is to always double check the fuel grade indicator on the pump before filling up.

Below are some indicators to be wary of that can increase the risk of mis-fueling;

  • You use an unfamiliar filling station – don’t assume hose colours are the same as your ‘local’ site
  • You switch between brands using different hose/nozzle colours
  • You swap cars (using different fuel) at home or work – it’s easy to ‘forget’ which car you’re filling
  • You hire a car using different fuel to your normal car
  • You buy a new car using different fuel to your old car
  • You continue a conversation with passengers while filling up
  • You are in a hurry/running late

PUT THE WRONG FUEL IN YOUR CAR?

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