WRONG FUEL FAQS
What do you do if you put the wrong fuel in your car?
DIESEL IN PETROL
What happens to a Petrol car filled with Diesel?
The diesel pump nozzle is larger than most petrol filler necks, so it doesn’t fit. That makes it considerably less common to put the wrong fuel in a petrol car than filling a diesel car with petrol.
Plus, it’s not as dangerous for a petrol engine to have Diesel in it, so there’s typically not as much damage.
Here’s what occurs when you put Diesel in a petrol car:
- Petrol fuel ignites by a spark from the vehicles spark plugs.
- Diesel in a petrol engine then jams up the spark plugs and fuel system.
- That means the car will not start.
It’s an annoying mistake. But it’s not as severe as the damage that petrol can cause to a diesel engine. Your petrol engine shouldn’t have any permanent damage once the fuel’s drained out.
How will I know if I have put Diesel in my Petrol car?
- The most common Diesel in petrol car symptoms are:
- The engine will start to misfire.
- The car will be challenging to start.
- The vehicle may stop, and the engine might keep cutting out.
- The exhaust and engine might produce smoke when driving.
What to do if you put Diesel in a petrol car?
Have you turned the ignition yet? If not, then don’t!!
The most severe damage from misfuelling happens after turning on the ignition.
So if you realise you have put Diesel in a petrol car before starting your engine, you’re in luck. Here’s what you should do:
- Leave your engine turned off and avoid putting your key in the ignition.
- Let the staff at the fuel station know what’s occurred.
- Put the car into neutral.
- Push the vehicle to a safe place.
- If you are in London, call Fuel Hero.
What should I do if I have driven my car filled with petrol instead of Diesel?
If you’ve started your engine after fueling up with Diesel instead of petrol you should:
 
- Turn off the engine immediately if and when it is safe to do so. If not, pull over to a safe spot as soon as you can.
- Call Fuel Hero, Now.
PETROL IN DIESEL
I drove my diesel car a short distance after I filled it up with Petrol, then it just died on me. Will it need to be repaired?
Chances are you didn’t drive it for a short distance on Petrol what’s more likely is that you drove it for a short distance with Petrol in the fuel tank.
Once the Petrol made its way up through the low-pressure sender pump, through all the fuel lines, up to and through the filter, through the fuel lines to the high-pressure pump, then through the pump itself, into the common rail reservoir, and finally into the high-pressure lines into the combustion chamber, that’s usually the exact point that the engine comes to a stop.
In fact, you will find you actually only got about 40 yards on Petrol, which is the time it took for the engine to stall.
The good news is, this isn’t as catastrophic as you might think and there is a simple, effective solution in a mobile fuel drain – a service we provide all over London and we attend most call outs with the hour, 24 hours a day.
Call Fuel Hero – NOW!
What happens to a diesel car filled with Petrol?
Putting Petrol into a diesel vehicle can cause more damage than diesel in a petrol vehicle.
Putting Petrol in a diesel vehicle is more common because petrol nozzles can easily fit into most modern diesel filler necks. It makes it far simpler to put Petrol into a diesel tank than vice versa accidentally.
Petrol damages diesel engines because:
- Diesel acts as a lubricant, supporting the fuel pump to do its job.
- Petrol does the opposite – it enhances friction between parts in the diesel engine.
- The enhanced friction is not good news for your diesel engine.
- The more Petrol that is pumped through the diesel engine, the more damage it can do.
- That’s why it’s vitally important not to start the car.
Common rail (or HDi) diesel engines are especially likely to be damaged by the wrong fuel. If there is a lot of damage, it could mean new fuel pumps, injectors, pipes, filters, fuel tank – or at worst even a whole new engine.
Don’t worry, though, Call Fuel Hero – We will save your car!
How will I know if I have put Petrol in my diesel car?
The most common symptoms of putting Petrol in a diesel car are:
- The engine will make a loud knocking sound while accelerating.
- The exhaust will produce excessive smoke than usual.
Engine idling will be rough. - Acceleration will become problematic.
- The engine warning light may come on, and the engine may stop.
- The vehicle may be difficult to start again, especially when warm.
Are you unsure? Call Fuel Hero we will be happy to advise you.
How will I know if I have put Petrol in my diesel car?
Have you turned the ignition yet? If not, then don’t!!
The most severe damage from misfuelling happens after turning on the ignition.
So if you realise you have put Petrol in your diesel car before starting your engine, you’re in luck. Here’s what you should do:
- Leave your engine turned off and avoid putting your key in the ignition.
- Let the staff at the fuel station know what’s occurred.
- Put the car into neutral.
- Push the vehicle to a safe place.
- If you are in London, then call Fuel Hero.
What should I do if I have driven my car filled with Petrol instead of diesel?
If you’ve started your engine after fuelling up with Petrol instead of diesel you should:
- Turn off the engine immediately if and when it is safe to do so. If not, pull over to a safe spot as soon as you can.
- Don’t Worry or Panic.
- If you are in London, then call Fuel Hero, Now.
Other FAQs
My car has cut out, have I ruined it?
No, your car “cutting out” is your engines way of saying “I am not starting until you get the wrong fuel out of me”, Fuel Hero attends many “conk outs” “died” “made horrible noises” etc. Once the tanks & fuel systems have been drained, 20 litres of correct fuel put in – and the system fully purged up to the high-pressure pump fuel inlet – then, 99% of vehicles are absolutely fine.
I have put the wrong fuel in my car, have I damaged it?
Thankfully, it is doubtful that you have. Pretty much 99% of callouts Fuel Hero attend are up and running again when drained & flushed correctly; if you have not started your car, you will not have damaged it. If you have driven your car, then the chances of any lasting damage are still very slim.
Cant I just top my vehicle up with the correct fuel?
This is a difficult one for us to answer, Fuel hero would always recommend a full fuel drain, not because we want your business but because Petrol is not any good in diesel engines.
It can potentially corrode rubber hoses and plastic seals that are fuel type-specific (Petrol and diesel behave differently on different materials.
Car manufacturers use various plastics and rubber in the fuel system), as much as we believe wrong fuel will not ruin a car, that is based upon the wrong fuel being taken out correctly as soon as the mistake has been spotted.
Petrol in a diesel engine will eventually cause problems if not dealt with, but if you are driving an old banger that will be scrapped when it fails its MOT that is due in a month or so then you might as well risk it, but otherwise to avoid sleepless night and potential huge garage bills, we recommend just having it drained.
Will my insurance cover the cost of my misfuel?
Yes, some insurance companies do, its always best to check with them first.
Others offer excess type insurance like your windscreen cover, where you will pay them an amount, and they will, in turn, send someone like us out to drain the tank.
Does my fuel filter need to be changed after I put the wrong fuel in?
We always advise you to check with your manufacturers misfuel policy; in most cases, we rarely change the fuel filter as our equipment can flush it out.
If the wrong fuel has been in your car for longer than 72 hours, then we advise you to have it changed.
What happens to the fuel you take out my vehicle?
We unload our mixed fuels into our local recycling depot. We have large storage tanks situated here.
Every month an approved operator will collect this from us, and put it through a recycling process.
Chances are in a few months you may be using your own fuel again, as after it is recycled its sold back to fuel stations.
Can I keep the fuel you take out my vehicle?
Unfortunately due to SEPA legislation, we cant. Even if you have approved containers and a waste transfer note, our fuel draining tanks cant be dismantled and the fuel can only be dispensed into our equipment.
Can I use Petrol in the winter for a fuel additive?
Yes, Petrol can be used as a winter fuel additive, in remote freezing areas that do not have a well-established supply of fuel and previously in the UK before suppliers developed additives to do the same but a better job.
Engines that can tolerate a bit of Petrol are lower technology diesel’s that do not have the high-pressure pumps that are found in today’s cars. We would not recommend using Petrol as an additive to diesel.
Do Petrol & Diesel mix?
If you have mixed fuel in your vehicle, do not think that there is a more significant or lower portion of either fuel at the bottom where it feeds into the pump.
- Petrol weighs 737.22 grams per ltr
- Diesel weighs 840 grams per ltr
When diesel and petrol mix they combine and cannot be parted by taking fuel off the top or bottom. When you put the wrong fuel in a vehicle, it mixes in no distinct order; some may state that the diesel will sink to the bottom, or the Petrol will float to the top, this is certainly not the case.
We have had mixed fuel tested various times, and samples were taken from the top and bottom of our storage tanks after they had sat for a period of weeks, the mixed fuel taken from the top has more Petrol in it, but still contains diesel. The mixed fuel removed from the bottom contains more diesel but again still has Petrol in it.
I have only put £10 in my tank, can I just top it up?
This answer depends on the size of your tank, if you were driving an HGV with a 300l fuel tank, then the answer would be yes, if you were driving a fiat 500 with a 38l fuel tank, then no.
We deal in %, anything above 5% of the capacity of the tank starts to become a dangerous mix (Example 2.5L in a 50L fuel tank). Anything over 10% of the capacity of the tank must be drained.
How much of the wrong fuel can I get away with?
We recommend draining anything over 5% of the capacity of your tank.
How many put the wrong fuel in each year?
The AA released figures stating that around 300,000 misfuel per year, that’s approximately one every two minutes in the UK.
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