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.
