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What To Do If You Put The Wrong Fuel In Your Car

You Have Put the Wrong Fuel in your Car? Don’t Panic, Do This 

Hopefully, you've noticed while still at the bowser and haven't driven anywhere in which case you might be able to simply drain the tank, refill with the right fuel and be on your way but if you run the car at all, you could be in trouble. 

The problems of putting the wrong fuel in your car differ between what you should have put in. A diesel engine uses fuel designed to ignite on compression and petrol engines use spark and because of this, the fuels are very different. Diesel is designed or tuned to ignite at quite specific compression ratios, diluting it with petrol can lead to early ignition which can be damaging to the engine. Accidentally adding diesel to a petrol engine can cause the opposite with the fuel not igniting properly causing reduced power and possibly damage through no combustion at all but that's not all. 

Modern engines use high-pressure injectors to spray very accurate and measured fine mists of fuel into your engine. These injectors are designed for some variance in fuel but not to the degree of difference in diesel and petrol. Some injectors can become clogged or blocked by the wrong fuel leading to costly replacements. 

If you noticed you’ve put the wrong fuel in and you haven't started the car, don’t. There is a decent chance you’ll be able to drain the tank and refill it with the right fuel and be OK. A person handy with common tools can do this yourself just remember to don the right protective gear and dispose of the waste fuel appropriately. 


You've Driven Away and the Car Stopped

You’re in trouble. If you’ve filled up, hit the road and either come to a complete stop after the engine died or you’ve noticed it running rough, the wrong fuel has already made it inside your engine's vital systems. 

If you have an old petrol engine that relies on basic injectors, you might be able to flush your system, check your spark plugs and be all right but with a modern engine with sophisticated injectors, you are likely looking at the need to replace or overhaul them as well as a flush of the fuel system but with petrol engines, the likelihood of damage is not as high as petrol in a diesel engine as the fuel is less likely to ignite, not more so like in a diesel engine. 

If you’ve found out too late that it's petrol where diesel should be, you could be in for more trouble. Diesel engines switched to high-pressure injectors a lot longer ago than petrol engines to lower emissions and increase efficiency. It is rare to find a mechanically pumped diesel engine newer than the early 90s. The bad news is that your fancy injectors will need to come out and be cleaned and you’ll need to flush your system but as a petrol-diesel mix can ignite early in the engines cycle, you may have caused serious damage - this will be fairly obvious through terrible rattling, a sudden locking of the engine (seizing) or even some of the insides of the engine blowing out the side. You do not want this to happen, obviously. 


What Should I Do Then?

Call for help. Either get onto Roadside Assistance, a business such as Wrong Fuel Rescue or a friend with a trailer and head to a mechanic. Some fuel stations have kits available to help you drain your fuel tank safely. If your car is under warranty, definitely get onto them and check your insurance too as most do not cover accidental miss-fuelling of your car so it could be on you if there are costs involved.


  • KRC: August 31, 2022

    I mistakenly put petrol into my Diesel engined truck many years ago. I had to travel many miles with the engine running roughly but it didn’t dawn on me about the wrong fuel. The consequences were that I caused $15,000 damage to fuel pump, fuel lines and injection system to a nearly new truck. My insurance company rejected a claim but after I badgered them that it was an accident as much as driving into a wall they relented and paid out the claim. I was lucky, not sure if that would work nowadays.

  • Gerry: August 31, 2022

    I have personally made this my mistake. I still had 1/2 tank of fuel but was going to a remote area without any fuel within 200 kilometers. So I filled up t the last town and went on my merry way towing a pop up caravan. . My vehicle a 2003 Nissan Navara,Diesel. started up fine and was able to drive for 70 plus kilometers when we decided to make a rest stop. This was on a Saterday after noon. I did not really notice much untill I had to go slow because of road conditions but the motor kept running ,albeit was quite right. When we reached the area where we wanted to stay I turned of my engine and walked around to find a suitable spot to set up. Went to start up he engine and NO WAY, it would not start. I could smell petrol and it still did not hit me that I put in the incorrect fuel. I looked under the bonnet , saw nothing. Went around the back and thesmell became stronger near the exhaust. That’s when it hit me, so I took the cap of the filler and yep petrol in the tank.After a ten kilometer walk before I could find a farm where I was allowed to use their phone to call a tow truck to take me to the nearest mechanic in the small town where I filled up. The driver put the nissan on the tray and my caravan on his towball. The truck operator rang a few people and found someone who could fix the problem. But because of the time could not do it till the next day. A Sunday… The truck driver found a spot to park the caravan where we could stay the night. There were no camping areas in the small town but he found a spot near a local football too far away from the repair shop. Next morning at the workshop we were told the bad news. All the fuel line had te be removed , injectors and he cleaned the injector pump by just pumping diesel through it till it was clean.
    He drained the fuel completely and placed it in drums for disposel. The truck driver grabbed some fuel cans and went and bought some DIESEL . Some 4 plus hours later he started the car and all was well. Luckily I was able to transfer the cost (just under $4000). This included the tow from the bush camp to the garage. This happened about 10 years ago. I hate to think what the cost would at todays prices.
    The lesson I learned was make sure you pick up the correct nozzle. The black colour rather then yellow coloured nozzle does not necessarilly mean Diesel pump and not all garages in the out back have that safety leaver on the diesel pump Now lessn learned I still chack twice before picking up the ful nozzle. I still have my Navara and 410000 kilometers is still running well, but only on Diesel fuel. Know the old saying
    “LOOK BEFORE YOU LEAP” Happy travels everyone.

  • Robert: August 31, 2022

    You don’t talk about Add Blue in a diesel engine! In 2021 at Yunta just inside the SA Border we accidentally put add blue in our diesel tank, point 8 of a litre. The regular diesel bowser was out of action and a sign said to go to the truck bowser. What appeared to be a low flow hose was in fact add blue and very poorly marked. Standing up close to the bowser you couldn’t see the add blue label. The blue nozzle was so grubby it was black. They tried to act dumb so we would move out of the way. I refused. When talking to the tow truck owner he made the statement that they had had several people do this exact same thing recently. What does that make you think? There was a real problem for which the servo owner should have been responsible. Our insurance paid for the repairs under accidental damage cover. They should have found the other unfortunate people and sued the servo. Class action. Cost us over two weeks lost travelling. The insurance also paid our caravan park fees plus offered a hire care under our policy. The big holdup in the repairs was the accessor who took forever to do his job. With a followup questionnaire I said they should sack their accessor.

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