How to Fix Putting Petrol in a Diesel

Accidentally putting the wrong fuel can mean disaster for your engine and your wallet. If you’ve reached for the wrong pump by mistake, we’ve got a helpful guide on what to do so you don’t end up stranded at the petrol station.

Why it's Bad

Other than the fact that your cars manufacturer tells you not to do it – diesel specifically lubricates the engine so that everything flows smoothly. So when petrol runs through, and the moving parts aren’t given what they need from the fuel, you risk the engine block seizing up – which could end up costing you thousands of dollars to replace the engine.

Put Your Key Back in Your Pocket

If you manage to catch yourself at the pump – you’re lucky. Whatever you do, don’t try and start the car! Just put your key away.

Even if you don’t start the car, some cars take the key being put in the ignition as a signal to prime the engine and get ready to drive. And if you’ve put the wrong fuel in, petrol ends up going through the diesel engine even if you’re just sitting there.

Some cars that have keyless entry or push-button start features, take opening the doors as the signal to prime the engine – so if you’ve caught yourself at the pump, just call roadside assistance.

Pull Over

If you’re driving, and you realise something’s wrong with the car – pull over as soon as it’s safe.

Common signs you’ve put the wrong fuel in may be a car that’s hard to start, rough running, a smoky engine or exhaust or in the worst cases, a sudden or complete loss of power.

If you notice any of these things, pull over, put your hazard lights on and call your roadside assistance, a mechanic or a tow-truck.

How to Fix It

In either case, your cars fuel tank will have to be drained and depending on where you realised, the fuel pump, injector, fuel rail and other parts may have to be replaced. Basically, the further the fuel goes in the engine, the more expensive.

Some say that a tiny bit of petrol in a diesel tank is fixable – that an engine can tolerate up to 10% contamination. This may have been true of older diesels, which were adapted from trucks and machinery; but as diesel engines have become more refined for efficiency and environmental reasons, they have become much less tolerant of mixing fuel.

Common-rail diesels (CRD) and Gasoline-direct injection (GDi) diesels are particularly susceptible to catastrophic damage if petrol goes into the tank. If you catch it early enough, drain the fuel tank and refill – you shouldn’t experience any more problems.

Will Warranty Cover the Damage?

Generally speaking, manufacturers don’t cover the costs when you put the wrong fuel in. The best you can expect from your manufacturer warranty is for a tow-truck to take you to a service centre.

If you’re unsure whether your manufacturer will help you out in case of misfuelling, talk to the friendly team at Motorama to find out about warranties and roadside assistance that some of our brands offer.

And if you have put the wrong fuel, make sure you follow our guide and hopefully, you’ll have caught it before it does any major damage.

But to be on the safe side, bring your car into a Motorama Service Centre, where Motorama’s expert technicians can see if there’s any long-lasting damage and tell you what to do from here.