A full 2026 guide to putting petrol in a die5sel car.
Putting petrol in a diesel car is one of the most common fuelling mistakes in the UK. Many drivers worry they have only added a small amount of petrol in diesel and wonder if it will be safe to drive. Unfortunately, even small amounts of petrol can cause problems in modern diesel engines.
Diesel fuel provides lubrication to vital components such as injectors and the fuel pump. Petrol does not provide this lubrication. If petrol enters the diesel system, it can increase wear, cause poor engine performance, and lead to expensive repairs if not dealt with quickly.
If you have put petrol in a diesel car, the safest action is not to start the engine and arrange professional petrol in diesel recovery as soon as possible.
What Happens If You Put Petrol in a Diesel Car?
When petrol is added to a diesel vehicle, it changes the properties of the fuel inside the tank. Diesel engines rely on thick fuel for lubrication, whereas petrol is thinner and more abrasive to diesel components.
If the engine is started after petrol is added:
- Petrol circulates through the fuel system
- Lubrication is reduced
- Injectors and the high-pressure fuel pump may be damaged
- Long-term engine damage can occur
This is why petrol in diesel problems should always be treated as an emergency, even if the car seems to run normally at first.
Petrol in Diesel Symptoms to Look Out For
If petrol has already entered the system, common petrol in diesel car symptoms include:
- Difficulty starting the engine
- Engine knocking or rattling noises
- Loss of power while driving
- Excessive smoke from the exhaust
- Engine warning lights appearing
If any of these symptoms occur, stop driving immediately. Continuing to drive with petrol in diesel increases the risk of serious damage.
