What happens if you put petrol in a diesel car?
Putting petrol in a diesel is the most common — and most damaging — misfuel in the UK. Here's what actually happens, and what to do if it's just happened to you.
Why petrol harms a diesel engine
Diesel doubles as a lubricant for the high-pressure pump and injectors. Petrol is a solvent, so it strips that lubrication away. If the engine is run, metal-on-metal wear can damage the pump and send debris through the fuel system — the repair most people are trying to avoid.
The single most important thing
Do not start the engine. If the key hasn't been turned, the petrol is just sitting in the tank and a drain-and-flush almost always avoids any lasting damage. Every start and every mile increases the risk and the cost.
What we do
We come to you, extract the contaminated fuel, flush the lines and filter, add clean diesel and test-start the car — usually in 45–90 minutes, and you drive away.