Petrol in a diesel? Don't start it.
The most common misfuel, because a petrol nozzle fits a diesel filler easily. Caught before the engine runs, it's usually a straightforward drain and flush.
What we actually do.
Switch "Engine started?" to Yes to see why stopping straight away matters.
How we fix itPick what happened, then press and hold the button.
1 · Drain the wrong fuel
Ignition off
Keep it off until the fuel's drained.
A simplified view of a real job. Every vehicle is different, so call us about yours.
Then we clean the lines.
If the engine ran, the wrong fuel isn't just in the tank. It's in the fuel lines, the filter and the injector rail too.
Cleaning the fuel linesIf the engine ran, the wrong fuel is in the lines, the filter and the injector rail, not just the tank. Hold the button to flush it through.
Contaminated fuel in the lines
Clean fuel is pushed through from the tank end and the contaminated fuel comes out into a sealed jar.
What happens
Diesel helps lubricate the parts of a diesel fuel system, including the high-pressure pump and injectors. Petrol thins the diesel out and doesn't lubricate in the same way. While it's sitting in the tank it does no harm; the risk starts once it's pumped through the system. That's why leaving the ignition off matters so much.
Signs if it's been driven
If you didn't notice at the pump, these are the usual signs. Pull over safely, switch off and call us.
- Knocking or rattling from the engine
- More smoke than usual from the exhaust
- Loss of power or jerky acceleration
- Engine warning light on
- Rough running or stalling
- Won't restart after stopping
How we fix it
We drain the petrol and diesel mix from the tank, flush the fuel lines and refill with clean diesel so you can drive away.
- 1
Drain
We pump the wrong fuel out through the filler neck, fuel lines or sender unit.
- 2
Flush
We flush the fuel lines so contaminated fuel isn't left in the system.
- 3
Refill
The right fuel goes in. Fill to at least three-quarters to dilute anything left.
- 4
Drive
Receipt sent to your phone. Book a new fuel filter at a garage soon.
Afterwards
- Fill to at least three-quarters with the right fuel to dilute any small trace left.
- Have the fuel filter replaced at a garage as soon as you can.
- If a warning light stays on, or it runs roughly, stop and get it checked, and let us know.
- Keep your receipt for any insurance claim.
Questions
How much petrol is too much?
There's no safe rule we'd stake your engine on. It depends on the vehicle and how full the tank was. Call us and we'll advise; don't start it to find out.
Can I just fill up with diesel to dilute it?
We wouldn't. Diluting doesn't take the petrol out, and running a modern diesel on a mix risks expensive damage. Draining is the safe option.
I drove a few miles before I noticed. Is it ruined?
Not necessarily. Pull over, switch off and call us. We'll drain and flush, but we can't promise to undo any damage already done before we arrived.
We fix all of these.
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The four things to do in the next five minutes.
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