Put Wrong Fuel in Your Car? Here's Exactly What to Do

Summary

• Don't start the engine: This is crucial. If you haven't turned on the ignition, the damage can be minimal.
• Get the tank drained: Call a fuel drain service or your breakdown cover provider. They'll remove the wrong fuel and flush the system.
• Cost: A fuel drain typically costs £150-£300. Starting the engine with wrong fuel can lead to repair bills of £3,000 or more.

It happens more often than you'd think. You're tired, distracted, or in a rush. You grab the pump and start filling up. Then that horrible sinking feeling hits.

Wrong fuel.

Don't panic. What you do in the next few minutes makes all the difference. Follow this guide and you can avoid serious damage to your car.

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The Most Important Rule: Don't Start the Engine

This is the golden rule. If you realise your mistake before turning on the ignition, you're in a much better position.

Here's why: Modern fuel systems are designed for one type of fuel. The wrong fuel can damage sensitive components like fuel pumps, injectors, and the engine itself.

But this damage mainly happens when the engine runs and pumps the wrong fuel through the system.

Key point: Don't turn on the ignition. Don't even put the key in and turn it to the "on" position. This can activate the fuel pump and start circulating the wrong fuel.

What If You've Already Started the Engine?

If you've already started driving, pull over as soon as it's safe to do so. Turn off the engine immediately.

You may have noticed something was wrong. The engine might have:

• Run roughly or misfired
• Lost power
• Made unusual noises
• Produced excessive smoke
• Cut out completely

The sooner you stop, the less damage you'll cause.

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Petrol in a Diesel Car: The More Serious Problem

This is the more common and more serious mistake. Diesel pump nozzles are larger than petrol ones, so they don't fit easily into petrol cars. But petrol nozzles fit fine into diesel tanks.

Putting petrol in a diesel car can cause significant damage because:

• Petrol acts as a solvent: It strips away the lubrication that diesel provides. This damages the fuel pump and injectors.
• Petrol ignites differently: Diesel engines rely on compression to ignite fuel. Petrol can cause misfires and engine damage.
• Modern diesels are sensitive: Common rail diesel systems are precision-engineered and very expensive to repair.

What to Do

1. Don't start the engine: If you're still at the pump, leave the car where it is.
2. Put the car in neutral: Ask for help to push it to a safe spot away from the pumps.
3. Call a fuel drain service: They'll come to you and drain the tank on-site. This usually takes about an hour.
4. Pay for correct fuel: Once drained, you'll need to fill up with diesel before driving away.

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Diesel in a Petrol Car: Less Common, Less Damaging

This mistake is harder to make because diesel nozzles are larger. But it does happen, especially with jerry cans or older pumps.

Diesel in a petrol engine is generally less damaging because:

• Diesel doesn't ignite easily in a petrol engine
• The engine will usually just run badly or not at all
• There's less risk of permanent damage to components

But you still shouldn't try to drive it. The fuel system needs draining just like with the opposite mistake.

What to Do

The process is the same as for petrol in diesel:

1. Don't start the engine
2. Move the car to a safe location without starting it
3. Call a fuel drain service
4. Fill up with correct fuel after draining

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How Much Does a Fuel Drain Cost?

The cost depends on where you are and what's happened:

Situation	Typical Cost
Fuel drain at petrol station (engine not started)	£150-£250
Fuel drain at roadside (engine started briefly)	£200-£350
Tank drain plus fuel system flush	£300-£500
Repairs after driving on wrong fuel (diesel car)	£3,000-£10,000+

As you can see, paying for a drain is much cheaper than paying for engine repairs. That £200 drain could save you thousands.

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Who to Call for Help

Breakdown Cover

If you have breakdown cover with the AA, RAC, Green Flag, or another provider, call them first. Many policies include wrong fuel assistance or can arrange a fuel drain for you.

Some policies cover the cost. Others will organise the service and you pay the technician directly. Check your policy documents or ask when you call.

Specialist Fuel Drain Services

There are companies that specialise in wrong fuel recovery. They operate 24/7 and can usually reach you within an hour or two.

Search for "wrong fuel drain" plus your location. Make sure to use a reputable company with good reviews.

The Petrol Station

Let the staff know what's happened. They deal with this regularly and can help you move your car to a safe spot. Some stations have contacts for local drain services.

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What Happens During a Fuel Drain?

When the technician arrives, here's what they'll typically do:

1. Access the fuel tank: Usually through the filler neck or by removing a cover under the car.
2. Drain the contaminated fuel: Using a pump to remove all the wrong fuel from the tank.
3. Flush the fuel lines: If necessary, they'll clean the fuel lines and sometimes the fuel filter.
4. Add correct fuel: They'll put in a small amount of the right fuel to get you going.
5. Start the engine: Test that everything is working properly before you drive away.

The whole process usually takes 30-60 minutes.

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Can I Claim on Insurance?

This is a grey area. Misfuelling is usually considered driver error, not an accident.

Standard Car Insurance

Most standard car insurance policies don't cover misfuelling. The drain service cost will come out of your own pocket.

However, if you've driven on wrong fuel and caused significant engine damage, you might be able to claim. Check your policy or call your insurer to ask.

Be aware that making a claim could affect your no claims discount and future premiums.

Fuel Card Protection

Some fuel cards and credit cards offer misfuelling protection as a benefit. If you paid with one of these, check if you're covered.

Breakdown Cover

As mentioned, some breakdown policies include wrong fuel cover. Others offer it as an optional add-on. This is often the most useful protection to have.

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How to Prevent It Happening Again

Once you've been through this nightmare, you'll want to make sure it never happens again. Here are some tips:

Simple Reminders

• Put a sticker on your fuel cap: A simple "DIESEL ONLY" or "PETROL ONLY" sticker is a visual reminder.
• Check before you pump: Make it a habit to look at the pump label and your fuel cap every time.
• Don't fill up when distracted: If you're stressed, tired, or in a rush, take a moment to focus.

Misfuel Prevention Devices

For diesel cars, you can buy a device that fits in the filler neck and only allows diesel nozzles (which are larger) to fit. Petrol nozzles are too small to open the mechanism.

These cost around £30-£50 and are worth considering if you're worried about making the mistake again, or if you share the car with multiple drivers.

Be Extra Careful With Hire Cars

Misfuelling is especially common with hire cars or cars you don't usually drive. Always check what fuel it takes before you fill up.

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Common Questions

How much wrong fuel does it take to cause damage?

Even a small amount can cause problems, especially in modern diesel cars. Don't think "it's only a few litres, it'll be fine." Get it drained regardless.

Can I just top up with the right fuel?

No. Diluting the wrong fuel doesn't fix the problem. The contaminated fuel still needs to be removed completely.

What if I put in E10 petrol by mistake instead of E5?

This is different from putting petrol in diesel or vice versa. Most modern petrol cars can use E10 fine. Only older cars (generally pre-2011) may have issues. Check your car's compatibility at gov.uk or with the manufacturer.

Will the garage know I used wrong fuel?

If you try to hide it and take the car to a garage with engine problems, yes, they'll likely figure it out. Fuel residue and damage patterns make it obvious. Be honest—it helps them fix the problem properly.

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Final Thoughts

Putting wrong fuel in your car is a stressful mistake. But if you act quickly and correctly, it doesn't have to be expensive or cause lasting damage.

Remember the key steps:

1. Don't start the engine
2. Move the car safely without starting it
3. Call for a fuel drain
4. Fill up with correct fuel
5. Drive away with a lesson learned

And next time you're at the pump, take that extra second to check. It could save you a lot of hassle.

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