E10 vs E5 petrol – which should you put in your car?

If your petrol car was built in the last 15 years or so, E10 is almost certainly the right fuel, and it is the cheapest petrol on the forecourt. E5, sold as super unleaded, is mainly for cars that cannot use E10 and for engines whose makers ask for higher-octane fuel.

The price difference is not small. On 11 October 2026, E10 averaged 174.7p a litre across the stations PetrolNearby tracks, while super unleaded averaged 192.2p. That is about 17.5p a litre more, or roughly £7.88 extra on a 45-litre fill.

What E10 and E5 actually mean

The "E" stands for ethanol and the number is the maximum percentage in the blend. E10 contains up to 10% bioethanol and E5 contains up to 5%. The rest is ordinary petrol, and both are made to the same British Standard for unleaded petrol, BS EN 228.

Bioethanol is alcohol made by fermenting plant sugars from crops. Blending it into petrol replaces some fossil fuel with a renewable one, which is why governments across Europe have pushed for higher ethanol blends.

You will see the grade on a label on the pump and the nozzle: a circle containing "E10" or "E5". Many cars also have a matching label inside the fuel filler flap showing which grades they accept.

How E10 became the standard

E10 became the standard petrol grade in Great Britain in September 2021, replacing E5 as the everyday 95-octane fuel. Northern Ireland followed on 1 November 2022.

E5 did not disappear. GOV.UK says it remains on sale as the 97+ octane super grade at many larger filling stations and at stations that sell two grades of petrol. Some rural, remote or very small stations may sell only one grade. In PetrolNearby's data, about three in four stations list a super unleaded price, compared with almost every station for E10.

Can my car use E10?

According to GOV.UK, all new cars manufactured since 2011 are compatible with E10, and about 95% of petrol vehicles on the road can use it. That leaves a minority that may not be compatible, including:

• classic, cherished and older vehicles
• some models from the early 2000s
• some mopeds, particularly those under 50cc

The simplest way to be sure is the government's online tool, Check if your vehicle can use E10 petrol, on GOV.UK. You choose the manufacturer and it tells you which models and years are compatible. You can also check your handbook, look for a label inside the fuel flap, or ask the manufacturer or a dealer.

The checker does not cover every brand. Many classic car manufacturers are not listed, and the government cannot give compatibility information for brands that no longer trade. If your vehicle is not listed, GOV.UK's advice is to keep using E5.

What if I put E10 in a car that is not compatible?

Do not panic. GOV.UK says a single tank of E10 in an incompatible vehicle should not damage the engine. Fill up with E5 next time and avoid using E10 over a long period. This is very different from putting petrol in a diesel car, which does need the tank drained before you drive.

Classic and older cars

The concern with older vehicles is not the fuel's performance but its effect on materials. Ethanol is a solvent and it attracts water, which can cause problems that modern fuel systems are designed to resist:

• Seals, hoses and gaskets. Some older rubber compounds, plastics and cork parts can swell, harden or break down with prolonged ethanol exposure.
• Metal parts. Ethanol and the water it absorbs can encourage corrosion in older tanks, carburettors and fuel lines.
• Loosened deposits. As a solvent, ethanol can loosen old varnish and debris in a tank, which may then block filters or jets.
• Storage. A car that sits for months is more exposed to moisture problems than one used every week.

If you own a classic, use E5 super unleaded unless you know your car is compatible. Owners' clubs and organisations such as the Federation of British Historic Vehicle Clubs publish fuel guidance for specific models, and a specialist garage can tell you whether parts of your fuel system have already been upgraded. Bear in mind that E5 can still contain up to 5% ethanol, so the same storage habits apply: keep the tank topped up, use the car regularly, and follow your club's advice on stabilisers if it is laid up.

Does E10 give worse fuel economy?

Slightly. Ethanol contains less energy per litre than petrol, so a fuel with more ethanol in it takes you a little less far. GOV.UK puts the effect at around 1% and says it is unlikely to be noticeable in everyday driving.

That 1% is far smaller than the price gap. Super unleaded costs about 10% more per litre than E10 on average, so for E5 to save money it would need to improve your economy by about ten times as much as the difference in energy content.

Here is a worked example for a car that averages 45 mpg on E5, assuming it does about 1% worse (44.6 mpg) on E10, at the UK average prices on 11 October 2026.

Even after allowing for the small loss in economy, E10 works out about 1.6p a mile cheaper, or about £127 a year at 8,000 miles. If you want to measure your own car's figures rather than rely on estimates, our guide to calculating mpg and cost per mile explains how, and the free fuel logbook will do the sums for you.

What octane means and why it matters

The octane rating (RON) measures how well petrol resists igniting too early under compression, known as knock. Standard E10 is 95 RON. Super unleaded is 97 RON or higher, and some brands sell 99 RON versions.

Higher octane does not contain more energy. It simply allows engines designed for it, often turbocharged or high-performance ones, to run more advanced ignition timing. Modern engines have knock sensors that adjust timing automatically, so a car designed for 98 RON will usually run safely on 95, but may produce slightly less power. A car designed for 95 RON gets little or no benefit from a higher number.

Your handbook will say which applies. Look for the difference between a minimum octane (the lowest the car can safely use) and a recommended octane (what the maker suggests for best performance).

When super unleaded makes sense

Paying the extra is reasonable in a few situations:

1. Your vehicle is not E10 compatible. This is the clearest case. Classic cars, some early-2000s models and some small mopeds fall into this group.
2. Your handbook recommends 97 or 98 RON. Some performance and turbocharged engines are designed for higher octane. You can use 95 if it is listed as the minimum, but you may lose a little performance.
3. The vehicle or equipment sits unused for long periods. Lower ethanol content means less moisture absorption, which can help with motorbikes, classic cars, boats and garden machinery stored over winter. Check the manufacturer's advice.
4. You want the extra additives. Branded super unleaded often comes with a stronger detergent package. Whether that is worth paying for is the same question we look at for diesel in is premium diesel worth it.

When it does not

For an ordinary modern car designed for 95 RON, super unleaded is unlikely to give you anything you would notice, and it costs about 17.5p a litre more on average. Treating your car to "the good stuff" every fill-up adds up quickly:

The gap also varies from station to station. In the middle 80% of stations, super unleaded ranged from 182.9p to 199.9p on 11 October 2026, so if you do need E5 it is worth comparing prices. On PetrolNearby you can search near you for super unleaded specifically, or browse prices by town.

E10, E5 and the bigger picture

The switch to E10 was part of a wider effort to cut carbon emissions from road transport, alongside the 7% biodiesel already in standard diesel (B7). For most drivers it made no practical difference beyond a new label on the pump. Prices since then have been driven by oil markets, refining margins and tax, as explained in how UK fuel prices are set, not by the change in ethanol content.

If you want to see how the price of standard unleaded has moved since 2003, our UK fuel prices page has the full government series, and our price charts show recent trends.

Frequently asked questions

Can I mix E10 and E5 in the same tank?

Yes. Both are petrol and they mix without any problem. If your car is E10 compatible, you can switch between the two freely. If it is not compatible, an occasional top-up of E10 will be diluted by the E5 already in the tank, but you should not make a habit of it.

Is E10 bad for my engine?

Not if your vehicle is compatible. Cars designed for E10 have fuel system materials chosen to cope with higher ethanol content. The concerns apply to older vehicles with parts that were never designed for it.

Why is super unleaded so much more expensive than E10?

Higher-octane petrol costs more to produce, it is sold in smaller volumes, and branded versions usually contain extra additives. Retailers also price it as a premium product. On 11 October 2026 the average gap was about 17.5p a litre.

Does E10 go off faster than E5?

Both petrol grades age over time, but ethanol absorbs moisture from the air, so fuel with more ethanol can be more sensitive to long storage. For a car you use every week this is not a concern. For something stored for months, such as a classic car, motorbike or lawnmower, E5 and the manufacturer's storage advice are the safer choice.

Will my car run better on super unleaded?

Only if it is designed for higher octane, and even then the difference may be small. If your handbook lists 95 RON as the recommended fuel, super unleaded is very unlikely to make a noticeable difference to performance or economy.