Petrol in a Diesel Car

Putting petrol in diesel cars appears to be the more common mistake than diesel in petrol cars because of greater familiarity with petrol cars. The larger diesel pump nozzles makes mis-fueling a little difficult. Whilst this could be as a result of being new to the vehicle or simply being distracted while filling up, knowing what to do in this situation can save you thousands. Serious issues that arise out of mis-fueling (putting petrol in diesel vehicles) – safety (petrol is extremely flammable), may cause serious damage to fuel injection system and the engine, the resultant damage is not covered under warranty and insurance policies may not provide cover for the mistake.

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 and create 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!

We recommend a full drain on any amount of contamination. We strongly recommend you call us first for out expert advice – we are here to help. A simple phone call could save you thousands of dollars in unnecessary repair bills.

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 contaminated diesel. It is essential to carry out a full drain. Once the contaminated fuel has been removed and the tank filled with the correct diesel 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.

With this situation, it is recommended to take every precaution to remove all of the contaminated diesel. 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 diagnositc check of the engine management system will be carried out to ensure no damage to the engine has been casued.

Reduce the risk

Always double check the fuel grade indicator on the pump before filling.

The risk of mis-fueling is higher if:

  • 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