Putting the wrong fuel in your car is more common than you might think. Whether it's petrol in a diesel car or diesel in a petrol engine, misfuelling can lead to costly repairs if not handled quickly. In this detailed guide, we’ll walk you through the dangers, signs, and immediate steps to take — and why fast, professional help is essential.

Common Misfuelling Mistakes in the UK

Each year, over 150,000 UK drivers accidentally fill up with the wrong fuel. The two most common mistakes include:

• Petrol in a diesel vehicle (most frequent)
• Diesel in a petrol vehicle (less common but still damaging)

Diesel fuel nozzles are usually larger, but some petrol pump nozzles can still fit into diesel tanks. Misfuelling often happens when:

• Driving an unfamiliar car
• Using a hire or company vehicle
• Being distracted or in a rush

Why It’s a Problem – What Fuel Contamination Does

Fuel systems are engineered for specific fuel types. Mixing fuels causes immediate and long-term issues:

1. Petrol in Diesel Engines

• Reduces lubrication
• Damages fuel pump and injectors
• Causes misfiring and stalling

2. Diesel in Petrol Engines

• Clogs spark plugs
• Causes starting issues
• Leads to excessive smoke and poor performance

Contaminated fuel can also damage the fuel filter, fuel lines, catalytic converter, and engine control system.

Do NOT Start the Engine!

If you realise your mistake before starting the car:

• Do not turn the ignition on.
• Inform petrol station staff.
• Call a mobile misfuel recovery specialist immediately.

Starting the engine circulates contaminated fuel throughout the system, making the damage worse.

Symptoms of Misfuelling

If you've already driven away before realising, watch for:

• Engine knocking or unusual sounds
• Lack of acceleration
• Excess smoke from the exhaust
• Stalling and restarting issues
• Dashboard warning lights

Immediate Steps You Should Take

1. Turn Off the Engine
   Pull over safely and cut the ignition to stop fuel flow.
2. Warn Other Drivers
   Turn on your hazard lights and place a warning triangle if you’re on a busy road.
3. Don’t Try to Fix It Yourself
   Avoid draining fuel manually. DIY draining can lead to fire risks and further damage.
4. Call a Professional Fuel Drain Service
   A mobile technician can come to your location, drain the tank, flush the fuel system, and refill with correct fuel.

Why Professional Help Matters

Professional misfuel services offer:

• Safe tank draining
• Fuel system flushing
• ECU diagnostics
• Disposal of contaminated fuel

Most providers, like CarBreakdownService.co.uk, offer 24/7 emergency assistance and can reach you within an hour.

How Long Does It Take to Fix?

Most misfuelling issues can be resolved within 30–60 minutes if the car hasn’t been driven. If the engine has been run, it may take longer due to the need for a full system flush.

Cost of Putting the Wrong Fuel in Your Car

• Without engine damage: £150–£300 for fuel drain
• With engine damage: £1,000+ for repairs

Acting quickly can save hundreds or even thousands of pounds.

How to Avoid Misfuelling Again

• Use coloured fuel caps or stickers
• Double-check before refuelling, especially if switching between cars
• Install a misfuelling prevention device
• Stay focused and avoid phone use while refuelling