Sometimes you know straight away that you've put the wrong fuel in. You look down at the nozzle and your stomach drops. But plenty of drivers don't notice at the pump. They pay, drive off, and only realise something is wrong a few kilometres down the road.
This guide covers the signs that point to misfuelling, how they differ between petrol in a diesel, diesel in a petrol car and AdBlue in the fuel tank, and what to do the moment you suspect it.
What to do right now
If you think you've used the wrong fuel, stop and act before anything else:
- If you haven't started the car, keep the engine off. Don't even turn the ignition on. On many modern cars, switching the ignition on starts the fuel pump, which pushes the wrong fuel further into the system.
- If you're already driving, pull over as soon as it's safe and switch the engine off. Don't try to "push through" to get home.
- Don't top up with the right fuel hoping to dilute it. It doesn't fix the problem.
- Call RoadHelp on 0498 338 188. We're available 24/7 and come to you.
Signs before you even start the car
The easiest time to catch a misfuel is before the engine runs. Check for these:
- The receipt. Your fuel docket shows the grade you paid for. If it says unleaded and you drive a diesel (or the other way around), that's your answer.
- The nozzle you used. Nozzle and hose colours vary between fuel brands, so don't rely on colour alone. Look at the label on the pump and nozzle.
- The fuel cap or flap. Most cars have a sticker inside the fuel flap showing the correct fuel. If it doesn't match what you pumped, don't start the car.
- A "wrong" smell. Diesel has an oily smell, while petrol smells sharper. A strange smell from the filler or the car can be a clue.
If any of these don't add up, leave the engine off and call. A car that hasn't been started is usually the simplest situation to deal with.
Signs of petrol in a diesel
This is the most common misfuel, because a standard unleaded nozzle fits easily into most diesel filler necks. Diesel also lubricates the fuel system, while petrol does the opposite.
Signs can include:
- Loud knocking or rattling from the engine
- Loss of power, especially when accelerating or going uphill
- More smoke than usual from the exhaust
- Rough idling or the engine cutting out
- The car stalling and being hard to restart
- An engine warning light on the dash
Symptoms may not appear straight away. Some cars run on the diesel already in the fuel lines for a short distance before problems start. Read more in our petrol in diesel guide.
Signs of diesel in a petrol car
This happens less often, because a diesel nozzle is usually larger than a petrol filler neck. It can still happen, particularly with jerry cans or some older vehicles.
Signs can include:
- The engine misfiring or running roughly
- Thick or smoky exhaust
- The car struggling to start, or not starting at all
- The engine cutting out shortly after filling up
- An engine warning light
See our diesel in petrol guide for more detail.
Signs of AdBlue in the fuel tank
Many diesel utes, 4WDs and vans have an AdBlue filler right next to the diesel filler, and sometimes under the same flap. Mixing them up is an easy mistake.
AdBlue should never go into the fuel tank. If the engine runs on it, you may notice:
- The engine running poorly or losing power
- Warning lights on the dash
- The car stalling or not restarting
Even if you haven't noticed any symptoms, don't start the car if you think AdBlue went into the diesel tank. Our AdBlue in fuel tank guide explains why this one needs care.
"I'm not sure" is a good enough reason to stop
Many drivers aren't certain. Maybe someone else filled the car, or you were distracted at the pump. If the car is behaving strangely right after refuelling, treat it as a possible misfuel.
Stopping to check costs you a few minutes. Continuing to drive on the wrong fuel can make the problem bigger. When you call, we'll ask a few simple questions, like what fuel went in, roughly how much, and whether the engine was started, to work out what's needed.
We come to you
RoadHelp is a mobile wrong-fuel rescue service, so you don't need to get the car to a workshop. We cover all of Canberra, including Belconnen, Gungahlin, Tuggeranong, Woden, Weston Creek, Molonglo, the Inner North and Inner South, plus surrounding NSW towns such as Queanbeyan, Yass, Murrumbateman, Goulburn, Marulan, Collector, Cooma and Jindabyne.
No membership is needed. The price depends on your location, vehicle, the time of day and whether the engine was started, so call for a quote.
Think you've used the wrong fuel?
Keep the engine off and call RoadHelp on 0498 338 188, 24 hours a day, 7 days a week.