What Happens When You Put The Wrong Fuel In A Car?
Written by: Simon Pavey, Last updated:27th January 2025
So, you’ve put the wrong fuel in your car. It’s a surprisingly easy mistake to make that plenty of drivers have made. In fact, What Car? It suggests that someone puts the wrong fuel in their car every three and a half minutes in the UK!
If you’ve put the incorrect fuel in your tank, acting quickly and effectively to resolve this issue is essential. Failure to do so could cause lasting damage to your vehicle. So, what are the next steps?
Is my car petrol or diesel?
To determine whether your car is petrol or diesel, you can start by checking the fuel cap or door, where the fuel type is usually indicated. Alternatively, consult your car’s owner’s manual or look at the vehicle registration document, which will specify the fuel type.
If you’re still unsure, the engine’s sound can provide a clue. Diesel engines are louder and have a distinct clattering noise, while petrol engines are quieter and smoother.
You can also check under the hood. Diesel engines often have a larger, more robust structure with additional components, such as turbochargers.
If you want to be absolutely certain, the best course of action would be to refer to the manufacturer’s details or visit a mechanic.
The impact of putting the wrong fuel in a car
The most important thing to do when you have misfuelled is not to start the engine under any circumstance. Starting the car with incorrect fuel in the tank could cause lasting, costly damage. The AA suggests that you remove the keys from the ignition immediately.
How much can it cost if you’ve put the wrong fuel in your car?
If you haven’t started the engine, the cost of having a specialist drain the fuel tank will be around £190, but if the motor is ignited, it could be closer to £5,000.
Try to get the car to a safe spot. Put the vehicle in neutral at a petrol station and push it to a safe place; you should get someone to assist you.
Call your breakdown provider immediately once your vehicle is in an appropriate location. They’ll have specialists available to drain your car’s system and make it safe to refuel again.
The impact of different fuel types on different car engines
Different fuel types have different properties and varying effects on a car engine.
Putting petrol in a diesel car
It’s incredibly easy to put petrol into a diesel car due to the size of the nozzle. Unfortunately, it’s also highly damaging to do this. What’s essential is not to start your car’s engine if you’ve made this mistake.
Check out our petrol insights here.
What happens if you put petrol in a diesel car
If you were to start your engine, you would likely hear a loud knocking noise when accelerating.
How far can you drive with petrol in a diesel car?
If your vehicle starts, you’re unlikely to get far, and it will quickly become apparent that something is critically wrong.
That’s because diesel acts as a lubricant that helps the fuel pump work as it should. Petrol, however, will increase the friction in your diesel engine, meaning the fuel pump will meet heavy resistance and become damaged. You could be looking at replacing the fuel pumps and other components or even replacing the entire engine if the petrol is allowed to wreak enough havoc on your vehicle.
What if I only put a small amount of petrol in a diesel engine?
If you’ve put a minuscule amount of petrol in your engine, it may run smoothly without noticing the impact. However, our recommendation is always to have your tank adequately drained. The risk of having an engine repaired is pretty substantial, so paying a small fee to drain an engine is probably a wiser decision in the long run.
Putting diesel in a petrol car – Will a diesel nozzle fit in a petrol car UK?
You’ll struggle to fit the diesel nozzle into a petrol car, so the chances of this happening are much lower. However, there are some instances where this accident can occur.
Putting diesel in a petrol car also causes less damage to the vehicle. The diesel fuel will clog the system rather than cause lasting damage.
What happens if you put diesel in a petrol car
You may quickly become aware that you’ve misfuelled your car as your engine starts to misfire – and there’s a good chance your vehicle won’t start at all. However, once the fuel is drained from the system, you can return to petrol, and everything should work as usual!
E10 in an incompatible vehicle and is my car E10 compatible?
In 2021, the UK transitioned from E5 to E10 petrol. This fuel contains 10% renewable ethanol, whereas E5 only includes 5%. This has helped the country significantly reduce its CO2 emissions—the equivalent of removing all the petrol vehicles from North Yorkshire!
However, some older cars are not compatible with E10. It’s estimated that around 600,000 vehicles on UK roads will not accept it.
Putting E10 in an incompatible vehicle shouldn’t cause too much damage. If you were to do this repeatedly, your vehicle’s internal structure could suffer due to the bioethanol’s corrosive properties.
You can also mix E10 and E5. Therefore, if you end up with an E10 in your incompatible vehicle, add some E5 as soon as possible.
How can drivers avoid misfuelling in future?
When drivers put the wrong fuel in their vehicles, it’s usually because they aren’t paying attention. This is easily done after a long day of work or an early start.
Remember that the colour of the hose and nozzle isn’t always consistent. If you’re at a fuelling station you aren’t familiar with, don’t just pick up the hose that is the colour you are used to using. Be sure to read the signage properly—the pump should specify whether it is petrol, diesel, or something else.
The AA suggests putting a reminder on the inside of the fuel cap to double-check that you are using the correct pump.
Why can’t I use my phone at a fuel pump?
It’s easy to be on autopilot whilst refuelling, but you don’t want to look up from your phone and realise you’ve had the wrong hose inserted into your vehicle!
Most forecourts have a strict policy where you are not allowed to use your mobile phone at the pump, and the attendant may cut off the flow of fuel if they suspect you’re distracted while refueling. This is to prevent possible damage to your car, and damage to the forecourt if you let fuel spill.
Find a fuel station near you by clicking here.
How can Fuel Card Services help?
You never know when an accident, such as misfueling, will wreak havoc on your vehicle. A maintenance plan is essential for catching issues before they cause further damage. That’s where MyService.Expert comes in.
With MyService.Expert, you can simplify your business’ vehicle maintenance with pre-negotiated rates at thousands of primary dealers and independent garages across the UK.
A proper service plan means less downtime and saves you hours of admin work.
Get in touch today to find out how we can help your business.
back
