Call us on 02890 020104   MyAXA

What do I do if I put petrol in a diesel car?

Putting petrol in a diesel car can cause severe engine damage. If you ever make this horrible mistake, it's important to act quickly.

Driving | Car Insurance

Kieran is on his way home from work, exhausted after a long day. He’s been rushing to meet a project deadline, and now that it’s in the bag, he can’t wait to get home. To save himself hassle in the morning, he stops at a filling station to fill up. Just as he’s replacing the pump, he realises to his horror: he has put petrol in his diesel engine. Instead of tearing his hair out, he phones a petrolhead friend for advice.

Man on phone after car breakdown

What to do

If you ever make this mistake, act quickly.

  1. Whatever you do, do NOT start your vehicle. Switching on the ignition will circulate the mixture of petrol and diesel through the fuel system. This contaminates other components.
  2. Call your mechanic. Explain the situation. Tell them the exact quantities involved. Each case is different; the age, condition and engine are crucial factors in determining how serious it is.
  3. If your mechanic recommends bringing the vehicle in, have the vehicle towed to the garage. To fix this problem, the tank will need to be drained.
  4. At the garage, the mechanic will drain the petrol from the fuel system, and if needs be, replace the fuel filter or maybe even the fuel tank.
  5. The mechanic will then safely dispose of the petrol.

The dangers of putting petrol in a diesel car

  1. Putting petrol in a diesel car causes severe engine damage to the injectors, which can be expensive to fix.
  2. Due to the difference in lubricity, fuel system damage is inevitable when petrol is run through a diesel system.
  3. Because they have different combustion points, engine damage is likely to result. In extreme cases, the engine may blow up.
  4. If the engine has been started with petrol, it will eventually stop running. This may result in further damage to the vehicle’s emission system.
  5. If you've noticed your mistake after a litre or two, simply fill up the rest of the way with diesel and use a diesel-specific additive for protection. If you've filled the whole tank, your only recourse is to drain it completely or risk substantial fuel system and engine damage.
Mechanic working on the underside of a car

The effects of misfuelling

  1. Diesel fuel pumps are lubricated by the diesel fuel itself. Mixing petrol with diesel creates a solvent, which means it reduces lubrication and can damage the pump through metal-to-metal contact.
  2. The more contaminated the system becomes, the more expensive it will be to repair. In extreme cases, it can be cheaper to fit a new engine.

How to prevent misfuelling

It’s easy to say the best way to avoid misfuelling is simply a case of always filling your tank with the correct fuel. However, mistakes are made. When we’re tired, we’re easily distracted. Here are some tips to reduce the risk of misfuelling:

  1. Always read the pump’s trigger label and the fuel grade indicator.
  2. If you’ve bought a new car and it has a different fuel engine than your previous car, leave yourself reminders in the car. A simple note on the dashboard that reads ‘Diesel, NOT Petrol’ is enough to stop you reaching for the wrong pump.
  3. When you’re at the petrol station, get rid of all distractions. Get off the phone; don’t chat to your passenger while you’re at the pump. It only takes a few minutes to refuel so give the task your undivided attention.
  4. If you’re hungry and can’t stop thinking about lunch, do not refuel the car. If you’re late collecting your kids from school, do not refuel the car. If you’re stressed about a meeting, do not refuel the car. When we’re hungry, in a hurry, or stressed, our minds are elsewhere and we’re more likely to make mistakes.
Different feul pumps

Around 150,000 UK motorists make this slipup each year; that's one every few minutes. When you stop at a petrol station to refuel, keep your mind on the task at hand. Filling your car with the wrong fuel can be a very expensive mistake!

Car Insurance

Looking for a quote?

Get a quote in under 5 minutes

Get a quote