E10 vs E5 Petrol: Which Does Your Car Need?

What E10 and E5 Mean

The "E" stands for ethanol, and the number is the maximum percentage of ethanol blended into the petrol.

• E10 contains up to 10% bioethanol mixed with 90% regular unleaded petrol. This is now the standard grade at every UK filling station.
• E5 contains up to 5% bioethanol. This is what "super unleaded" or "premium unleaded" is. It's the same fuel that was standard before September 2021.

Both are unleaded petrol. The only difference is the ethanol content. Diesel is unaffected by this change.

Why the UK Switched to E10

The switch was driven by carbon reduction targets. Ethanol is a biofuel, produced from crops like sugar beet and wheat. When blended into petrol, it reduces the overall carbon emissions from each litre burned. The government estimated that the move to E10 would cut transport CO2 emissions by 750,000 tonnes per year, equivalent to taking 350,000 cars off the road.

The UK was actually late to this. France, Germany, Finland, and Belgium had already adopted E10 years earlier. The US has used E10 as standard since 2010.

Can Your Car Use E10?

About 95% of petrol cars on UK roads are compatible with E10. If your car was built after 2011, it's almost certainly fine. The government's E10 compatibility checker lets you look up your specific make and model.

Cars That Can't Use E10

The main groups that should stick to E5 (super unleaded):

• Cars built before 2002. Many older vehicles have fuel system components (seals, hoses, gaskets) that aren't designed for higher ethanol content.
• Some cars built between 2002 and 2011. This is the grey area. Some are compatible, some aren't. Check the gov.uk tool or your owner's manual.
• Classic and vintage cars. Anything with a carburettor or older fuel injection system. Ethanol is corrosive to certain rubbers and metals used in older fuel systems.
• Some mopeds and motorbikes. Particularly older models. Check with the manufacturer.
• Certain lawn mowers, chainsaws, and other small engines. These often sit unused for long periods, and ethanol attracts moisture which causes corrosion.

What Happens If You Put E10 in an Incompatible Car?

A single tankful won't cause catastrophic damage. But repeated use over time can degrade rubber seals and hoses in the fuel system, cause corrosion of certain metals, and lead to fuel system blockages. If you accidentally fill up with E10, don't panic. Just use E5 for your next fill and going forward.

Performance and Fuel Economy

This is where people get frustrated. Ethanol contains less energy per litre than pure petrol. E10 has roughly 2% less energy content than E5, which means you get slightly fewer miles per tank.

In real-world driving, most people report a 1-2% drop in fuel economy with E10. On a 50-litre tank that costs £80, that's roughly 80p-£1.60 less range per tank. The savings from E10 being cheaper than E5 (typically 10-15p per litre) more than offset this small efficiency loss.

To put it simply: E10 costs less per litre but you use slightly more of it. You still save money overall compared to filling up with E5.

Does E10 Damage Engines?

In compatible cars, no. Modern engines and fuel systems are designed to handle E10 without issues. Every new car sold in the UK since 2011 has been tested and approved for E10 fuel.

The concerns are real for older vehicles, though. Ethanol is hygroscopic (it absorbs water from the air), which can cause corrosion in fuel tanks and lines. It can also dissolve certain types of rubber and plastic used in older fuel systems. If your car was built before 2002, or if it sits unused for long periods, stick to E5.

When Is E5 (Super Unleaded) Worth the Extra Cost?

There are a few situations where paying more for E5 makes sense:

• Your car isn't E10 compatible. This is the obvious one. You have no choice.
• Classic or collector vehicles. Even if technically compatible, many owners of older performance cars prefer E5 to minimise any risk to valuable fuel system components.
• Vehicles that sit unused for weeks or months. Second cars, motorhomes, boats. E5 has less ethanol, so it attracts less moisture during storage. Better yet, use a fuel stabiliser.
• High-performance cars where the manual specifies 97+ RON. Super unleaded is typically 97-99 RON vs 95 RON for E10. Some performance engines genuinely need the higher octane rating.

For everyone else driving a normal, modern car on daily errands and commutes? E10 is fine. Save your money.

Finding the Cheapest Fuel Near You

Fuel prices vary significantly between stations, sometimes by 10p or more per litre within the same town. Our Fuel Prices tool shows current prices at stations near you, so you can find the best deal whether you're filling up with E10, E5, or diesel.