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Petrol in diesel car

Unleaded in diesel car and driven with contaminated fuel
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We provide fast and reliable emergency mobile wrong fuel drain service. If you've mistakenly filled unleaded in diesel car, we can help! Our expert team is available 24/7 to assist you.

What happens when you put unleaded in diesel car?

Using unleaded in diesel car is a much more serious problem and could result in expensive and potentially permanent damage to your engine. Unleaded petrol will increase the friction between the various parts and components of your engine – unlike diesel which is a more lubricating fuel – and this is what will cause damage.


What to do if you misfuel your car

If you're lucky enough to realise you’ve put the wrong fuel in your car before starting your engine, do the following:

  1. Leave the engine switched off and don't even put your key in the ignition

  2. Inform the staff at the service station.

  3. You'll be advised to leave your car where it is, or it will be pushed to a safe place

  4. Call us to drain and flush the wrong fuel out of your car. We will be able drain and flush your vehicle's fuel system and get you on your way, unless there's more serious damage.


However, if you realise you've wrong-fuelled after you started up your car, both types of fuel will start circulating, damaging your engine. Here's what to do:

  1. If you’ve already started your engine, turn off the ignition immediately.

  2. If you're already moving, pull over to a safe spot, then switch off.

  3. Again, Call us to drain and flush the wrong fuel out of your car.

How to prevent misfuelling your car

  1. Stop and think when you arrive at a service station to refuel and don’t allow yourself to get distracted.

  2. Read the label on the pump and nozzle and double-check the information on the inside of your car’s fuel flap. A circular ‘E10’ or ‘E5’ label denotes petrol, while a square ‘B7’ sign means it's a diesel dispenser. ‘E’ stands for ethanol and ‘B’ for biodiesel.

  3. Check the colour of the fuel nozzle (black for diesel, green for petrol), but don't rely 100% on this colour coding.

  4. If you’re driving a new or unfamiliar vehicle, check and double check the labelling on the inside of the car’s fuel flap.

  5. If you're a diesel car driver, fit an adaptor which replaces the existing filler cap. This prevents you from accidentally putting a petrol nozzle into a diesel filler neck.

  6. If you’re still worried, the best way to avoid misfuelling is to put a sticker on the outside of the fuel flap reminding you which fuel is required.

Unleaded in diesel car symptoms

- Excessive/abnormal smoke (more excessive usual)

- Lack of power (slower than usual acceleration)

- Engine stalling/misfiring

- Struggling to start or not starting at all

- Unusual smell Petrol in Diesel give off distinctively different smells

- The engine management light illuminating

- Engine stopping altogether

Put unleaded in diesel car?

Turning the key is the biggest mistake you can make, as even if you don’t actually start the engine, illuminating the dashboard lights could mean your fuel pump whirrs into life. It’s supposed to prime the engine with diesel before it starts, but instead could be sucking the unleaded up the fuel lines. This means they’ll need draining and flushing as well as the fuel tank. If you get as far as starting the engine, there’s a whole lot more that can go wrong besides.

Unleaded in diesel tank: components

Modern diesel engines employ lots of technology to eke out their impressive mpg figures and minimise emissions, including expensive high-pressure fuel pumps, and common rail injectors with very fine tolerances.

Those fuel pumps are lubricated by diesel fuel itself, as it passes through. Replace that diesel with petrol, and its solvent properties mean the lubrication effect is eliminated too. A fuel pump running without lubrication will soon begin to create internal friction as its metal surfaces grind together. It will then begin to disintegrate, and that in turn creates swarf – potentially microscopic particles of metal that can do even more damage to your car's engine further down the line.

put unleaded in diesel car how much should I expect to fix it

The price variable. Depends on the vehicle's make and model and the location.

For instant quote, call our expert advisers and we can send our wrong fuel doctor out to your location  straight away if you've put unleaded in a diesel car.


Petrol in diesel engine

wrong fuel recovery services
Accidentally putting unleaded in a diesel car

Putting unleaded in a diesel car is far more serious than filling a petrol car with diesel.

Diesel cars use fuel as a lubricant, but petrol is corrosive so it can cause extensive damage.

Some of the main components that could be adversely affected by putting petrol in a diesel car include the fuel pump, fuel lines, fuel filter and fuel injectors.

The most common signs of a misfuelled diesel are that the engine will make a loud knocking sound whilst accelerating, sluggish acceleration, excessive exhaust smoke, idling will be rough, the engine warning light will illuminate, and your car might stall or struggle to restart.

How the unleaded harms a diesel engine
  • Once the unleaded petrol has stripped the lubricant out of the fuel pump, tiny fragments of metal from the parts rubbing together will enter the fuel system. Many of these will be caught by the fuel filter. However, some will make it all the way to the injectors and that’s when the real damage is done.

  • Modern diesel injectors work to very fine tolerances, releasing a fine spray of fuel into the cylinders. Even the tiniest foreign body will block the jets, throwing everything out of kilter. It could cause a misfire or the engine might even seize.

What happens when you put unleaded in a diesel car?

Putting unleaded in your diesel car may damage your fuel system if not dealt with properly. When you put petrol fuel in, the mix of petrol acts as a solvent, reducing lubrication and causing damage to the pump as the metal parts come into contact and rub together. Other parts of the fuel system which might not be compatible with petrol, can also be damaged. Switching on your car’s ignition will circulate this mix of petrol through your fuel system, causing further contamination to other components - not good! Ultimately, this could mean that the entire fuel system requires costly repairs, or replacing completely.

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