Filling up with the Wrong Fuel – What to do

Filling up with the Wrong Fuel


How many times do you fill up your car a week? Once, twice, three maybe? A straightforward and regular daily task can turn into a complete nightmare if you make the mistake of filling up with the wrong fuel. All it takes is a simple lapse in concentration at the pump, and the wrong fuel can be injected into your car’s veins. While you may think this will never happen to you, the fact is, it happens way more often than you may think.


Every day hundreds of motorists make the costly mistake of filling up with the wrong fuel. In fact, figures from the Automobile Association (AA) in the UK predict that around 150,000 people put the wrong fuel in their car every year. That equates to one person somewhere in the UK making the disastrous mistake every three and a half minutes.


So, what happens to your car when you fill up with the wrong fuel?


Putting Diesel into A Petrol Car

Putting diesel in a petrol car is far less common and not nearly as catastrophic. The diesel nozzle is generally larger than the petrol filler on most types of cars, which luckily, makes it tough to do. However, the AA has advised that this type of occurrence still accounts for one-third of its misfuelling calls.


The good news is this isn’t nearly as bad as you may think. Diesel is heavier than gasoline and requires pressure to be ignited, so chances are you won’t even be able to start your car. If your vehicle does start, the engine will run very rough with little power and lots of smoke, a sure sign you may need to pull over. However, not all is lost, the fuel system can still be flushed, fresh petrol put in, and your car should run normally again.


Putting Petrol into A Diesel Car

Putting petrol in a diesel car is much more disastrous and complicated to deal with. It is by far the most common occurrence, as the gasoline nozzle will easily fit into any diesel car. If you’re half asleep or not focusing when filling up, it can be an easy mistake to make (and potentially very costly).


Diesel fuel acts as a lubricant and helps to ensure the fuel pump runs smoothly. Mixing petrol with diesel that is already in your tank will result in the petrol acting as a ‘thinner’, and wreaking havoc on your car’s fuel system straight away. Petrol results in diesel losing its lubrication properties and wears down the engine and fuel pump through friction. The more petrol that is pumped through your fuel system, the higher the damage bill. You may even be required to replace the engine, fuel pump, injectors, filters and even need a new fuel tank.


What do you do if you put the wrong fuel in?

Don’t try to start your car! This is the biggest mistake you can make and even lighting up the dashboard can mean your fuel pump comes to life. If you own a diesel car, turning the key can result in petrol flowing through the fuel lines, which means they will need to be flushed and drained, in addition to the fuel tank.


If you pick up the mistake early when filling up your car, alert the attendant, put the car in neutral, push it somewhere safe and call your insurer. Your vehicle will need to be towed, inspected and flushed in a garage. If you do happen to drive away, you will notice pretty quickly as your car grinds to a halt. Call roadside assistance and explain the situation. Your vehicle will need to be towed, and the damage may be extensive.


How to prevent Filling up with the wrong fuel

First and foremost, pay attention when filling up. Most misfuelling occurs when you’re in a rush and not paying attention, so focusing for those few minutes at the petrol station can save you a lot of hassle, and money!

For more top tips, motoring and consumer advice, please visit the We Buy Motors Blog again soon. For more information on how to sell your car or for an instant online car valuation online visit


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