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What happens when you put petrol in a diesel car?

29th June 2023

Putting the wrong fuel in the fuel tank happens more often than you think. If you’re filling up on autopilot and have recently switched between the two, it’s an easy mistake to make. So, if you’ve filled up with the wrong fuel – don’t panic! What matters most is what you do next. This guide explains what to do if you put petrol in a diesel car or if you put diesel in a petrol car.

What should you do if you put the wrong fuel in?

If you put the wrong fuel in, the most important thing to do is to not turn your engine on and call your breakdown cover provider for roadside assistance.

What happens if you put petrol in a diesel car?

Putting petrol in a diesel tank can be especially damaging, particularly if you start your engine. Starting the engine forces the fuel through the system and can worsen the damage. This is because diesel and fuel have different properties.

Petrol is less lubricating than diesel, so when petrol circulates through a diesel car, it fails to lubricate important components of the vehicle like the fuel pump and injectors. Petrol causes damage to the fuel system, such as leaks and blockages.

Other issues can include ignition problems, because petrol has a lower flash point than diesel. It ignites at lower temperatures causing pre-ignition and engine damage. If you have a new diesel car, it’s likely to have a diesel particulate filter which feeds into the catalytic converter which petrol can damage.

What happens if you put diesel in a petrol car?

Putting diesel in a petrol car is generally less damaging than putting petrol in a diesel car. However, if you ignite your engine, it can still be damaging. It’s important to note that due to the higher flash point of diesel, you’ll probably struggle to start your engine.

Diesel is more lubricating than petrol which can cause more damage to the fuel injector and pumps. It’s also thicker and has a higher viscosity than petrol which can clog the fuel filter.

Here at Merityre, we’re able to support any of your motoring needs. For more information about the products and services we offer, simply locate your nearest Merityre branch or contact our friendly team to find out more.