More than one in seven of us have done it.
Men are twice as likely to do it than women.
Police officers are frequent offenders.
Misfuelling is the act of putting diesel fuel in a petrol car, or vice versa – and it occurs on average every four minutes. It can be humiliating, embarrassing and ultimately very costly.
Damaged cars will need flushing, may need several new parts, and on top of all this is the bill for the safe disposal of the contaminated fuel.
It has been estimated that UK motorists pay out more than £60 million in costs every year due to misfuelling mistakes.
Putting the wrong type of fuel in your car is a growing problem. On average, there are 150,000 misfuelling incidents which take place in the UK every year.
Why is misfuelling on the increase? There are a number of reasons why numbers are creeping up. Every year sees a rise in numbers of cars on the road. There are also more people in charge of more than one car – they may be insured on their partner’s car or driving a company car. This can lead to absent-mindedness when it comes to filling up on the petrol station forecourt.
Petrol in to diesel cars accounts for 95% of all misfuelling incidents. This is fairly understandable. In petrol cars, the fuel neck is narrower than a diesel nozzle, which makes putting diesel in to petrol cars difficult. However, it does happen, and the results can be quite serious.
Misfuelling has become such a problem that we’ve created a driver’s guide for what to do if you find yourself in this situation. We will answer all the questions, advise you on the best course of action and what to do going forward.
In this guide, we answer the following questions:
I’ve put the wrong type of fuel in my vehicle! What do I do?
Can I drive my car?
Who do I call for help?
What type of damage can the wrong type of fuel do to my car?
How much does it cost to fix?
What parts would need fixing?
What does a professional do that I can’t?
Can I get my fuel back?
Even if you haven’t misfuelled, we recommend you read this guide – it will act as a reminder at how costly and damaging misfuelling can be.
I’ve put the wrong type of fuel in my vehicle! What do I do?
The sooner you realise this, the better. Firstly, do not turn on your engine. This will cause the new fuel to enter the tank. This is when the damage starts. If your car is still on the garage forecourt, get help to push the car to a safe place out of the way. If your vehicle is an automatic, you will have to turn the key to put it in to neutral, so do this as quickly as possible.
Often, the driver will realise the mistake too late and the car will be in motion. The best course of action is to stop the car when it is safe to do so and call for help. The two different fuels will have different effects on car engines, so the method of getting the car re-started will differ slightly.
Petrol in a diesel car – modern automatic cars do not have a key that older cars have. So the car has to be started in order to take it out of park and disengage the steering lock. No massive problems should arise from the engine being on for a few seconds. A mobile fuel drain should be able to flush the car out and get it back up running safely with a top up of diesel.
If the car has been running, it must be stopped as soon as possible. Again, the tank must be emptied by a professional and an additive is used after the vehicle has restarted. At the very least, the fuel filter should be changed.
Diesel in a petrol car – again, the same should apply. However, there should be less room for damage. If the engine has been started, it will need a through flush through. The re-start might produce some black smoke – this will be the excess diesel residue burning off.
However, the best course of action in your particular situation must be decided by a professional. A misfuelled car is a danger on the roads and should not be moved once the mistake has been realised.
Can I drive my car?
No! Your car still has a chance of a quick recovery if the engine hasn’t started. If you have realised your mistake before starting your engine, you’re in a good position. Get help to move the car to a safe position, out of the way and call for help. The recovery job on your car will be far less painful if the wrong fuel has not yet had chance to enter your fuel lines. If you need to start the engine briefly to move it, it shouldn’t be too much of a problem.
Quite often though, you only realise your mistake when you feel your car is acting strangely while running. Stop in a safe position and call for help. Do not re-start the engine unless a professional advises you.
Who do I call for help?
Drivers who misfuel have a number of options available to them.
- A mobile fuel fix company
These provide a 24/7 mobile service, where they come to your assistance to flush out the engine. They dispose of the contaminated fuel, and add a small amount to the engine to keep the car going. This is the cheapest, quickest option and should normally be used if the engine hasn’t been started. However, this type of service cannot address any other issues, should the vehicle be unable to start.
- Recovery to a local garage
A garage will be able to flush the engine of the wrong type of fuel. They should also be able to identify any other potential problems if fuel has gone through the engine, and be able to rectify them.
- Recovery to a main dealer for vehicle under warranty
This is the most expensive, but most thorough way of fixing your car if the wrong type of fuel has gone through the engine. This type of service will be able to fix most issues that arise from misfuelling. A bigger bill is expected here, as the dealer may be replacing original equipment manufacturer (OEM) parts around the fuel storage.
What type of damage can the wrong type of fuel do to my car?
This all depends on how new the car is, and what type of fuel you have used. In newer models of cars, the engines are designed to cope with misfuelling a lot differently than old models.
Petrol in a diesel car can be more damaging than diesel in a petrol car. This is because petrol is more combustible than petrol.
In newer cars, electronic fuel management systems are able to identify whether the engine is running too lean (not enough fuel) or too rich (too much fuel). The system will then adjust the ignition timing and fuel injection accordingly.
However in older cars, carburetors regulate the flow of fuel and air in to the engine cylinders – and no automatic ignition timing exists. This means that there is much more room for damage in older cars and one or more of the following could happen:
A backfire – this is the most preferable outcome, and leads to the least damage.
The engine turns in the wrong direction – this could happen when the explosion takes place before the crank shaft is in the right position, which forces it back instead over the crest of the revolution.
A burnt piston – this is when the fuel burns too hot.
The latter two can be very expensive repairs when petrol runs through a diesel engine.
Diesel is less combustible, which means when it enters the engine, its effect on it is less dramatic. It doesn’t vaporise as well as petrol in a petrol tank, therefore it tends to flood the cylinders. In the rare event that the diesel does ignite, the engine will run heavy and sputter before coming to a stop. In most cases, a fuel filter and a couple of connection rods may need replacing.
How much does it cost to fix?
Misfuelling will always cost you – no matter how small the amount of fuel is that you put in. Of course, if you manage to realise your mistake before the engine starts, then calling out a mobile service will be the quickest, easiest and cheapest option. You will also be able to drive your car off the forecourt and try to forget this embarrassing and expensive mistake!
Mobile fuel drain cost: £175 – £300
However, if you’ve ran the engine, the car has been driven and the fuel has managed to work itself in to the system, then it is recommended that you get the car recovered and taken to a garage or your main dealer.
A garage will pick your car up, run through any associated problems, flush and drain the engine and replace any parts. However, unlike the mobile fuel drain, you will have to wait a little longer to get your car back if the garage has other jobs on and needs to order in new parts.
Local garage cost: £300 – £400
Heading to your main dealer to fix your engine is the safest bet – but definitely not the quickest or cheapest. Dealerships will perform a service which follows model protocol – replacing all original parts like for like. They will make sure that all equipment associated with the fuel storage and delivery system has been replaced according to manufacturer’s instructions. Depending on the make and model of your car, the price will vary accordingly. Sometimes your insurance can cover this, so it is worth checking your policy.
Main dealer cost: £2,000 – £10,000
What parts would need fixing?
Depending on the severity of the situation, you may either get away with not needing to replace anything, or have a hefty parts bill on your hands. For fuel that has not had a chance to enter the main part of the engine, a flush and empty will normally sort the problem out.
However, as we have learnt, that moment the main engine processes the foreign fuel is when real problems can occur. And the further the fuel gets, the more expensive the repair.
If the fuel is contaminated by pump wear debris, and gets as far as the common rail system, then the low and high-pressure fuel pumps, fuel rail, line filters, injectors, and fuel tank may have all have to be replaced – at some cost.
In severe circumstances, misfuelling has been known to cause entire engine replacements.
Here’s a quick video explaining what happens when you put the wrong fuel in a car engine:
What does a professional do that I can’t?
With something like misfuelling, we would always impress the importance of a professional carrying out the clean-up job rather than doing a DIY job yourself. Above everything else, you’ll need a waste carrier’s license to dispose of the contaminated fuel at the end anyway.
No matter how much you know about motors – give the responsibility to someone who does this type of thing for a living.
Going back to the three options available to someone who has misfuelled, we can look at their methods.
Option 1: Mobile fuel drain businesses have custom-made vehicles that comply with various UK safety rules. A mobile drain van comes with a 250+ litre tank designed to hold explosive substances. They will have ATEX-compliant pumps to handle diesel and petrol separately. They will also have numerous bits of kit on board including spill kits, booster starter packs and tanks containing a small amount of petrol and diesel supplies for the end-of-clean re-fill. The technician will be qualified (including fully trained on the Safety Passport Alliance, which enables someone to work safely with petrol). General protocol on a misfuelling job is to cone off the vehicle, pump out the contaminated fuel from the tank via the filler neck, restock and re-start. If the engine has already been run for a significant amount of time, the technician will carry out a flush on the fuel lines with the correct fuel, empty the tank, supply a small amount of the correct fuel and re-start.
Option 2: Local garages will arrange a recovery truck to collect your vehicle from its location and take it to the garage. Once there, a mechanic will take out the tank and drain it of the contaminated fuel. More fuel will be added once the tank has been reattached to make a re-start possible.
Option 3: Again, the main dealer will welcome the recovery truck in to its service centre. Here, it will carry out a full review of the engine, checking each part for any damage. Main dealers can be seen as over-cautious, but if you want a thorough job doing, this is the best option. The vehicle may be kept onsite for a few days while parts are ordered in and fitted.
Can I get my fuel back?
No. The fuel will be a mix – and therefore classed as contaminated. It is also useless in its current form. By law, it will need to go straight to a funded tank and then taken to a refinery where it will go through a process to separate the two types of fuel, and any other debris that has got in. Environment Agency rules state that this now clean fuel cannot return to you after it has left your vehicle.
However, there have been circumstances where the petrol station has been at fault. The tanker fills the tanks beneath the forecourts has sometimes filled the wrong ones. This means that drivers putting the correct pumps in to their tanks, were filling up with the wrong fuel. It doesn’t happen often, but when it does, the supplier will reimburse, and sometimes compensate, for this error.
The good news
The good news with misfuelling – you’ll only make the mistake once. A petrol station visit will never be the same, and a double (or triple!) check that the right nozzle is in use will be par for the course forever after. And with one in seven people in the UK guilty of it, you’re in good company!
Here are a few tips to avoid misfuelling going forward
TIP 1: For anyone else who is insured on your car, it may be useful to place an “UNLEADED-ONLY” or “DIESEL-ONLY” sticker by the fuel neck to remind them if they ever refill.
TIP 2: September and March sees an increase in new vehicles when the new registration plates come out. Spread the word about misfuelling so it is fresh in people’s minds. If you work in a business that supplies company cars to staff, speak to the fleet manager about misfuelling awareness training.
TIP 3: Misfuelling preventative devices are understandably becoming more popular. Looking at buying a new car? Certain makes like Honda, BMWs and Fords now come fitted with them as standard.
So next time you’re frantically searching google for “wrong fuel in car“, you’ll have a few tricks up your sleeve.