If you drive a petrol car in the UK, the green pump handle at most forecourts gives you E10: standard unleaded with up to 10% renewable ethanol. E5, with up to 5% ethanol, is now mostly sold as the premium "super unleaded" grade, and it usually costs a lot more.
For most drivers the answer is simple: buy E10. The rest of this guide covers the exceptions.
The short version
| E10 | E5 | |
|---|---|---|
| Ethanol | Up to 10% | Up to 5% |
| Usually sold as | Standard unleaded (95 octane) | Super unleaded (97+ octane) |
| Works in | Around 95% of petrol vehicles, and every new car since 2011 | All petrol vehicles |
| Typical price | The cheaper grade | Often 10p to 15p a litre more |
Can my car use E10?
Very probably. The government says around 95% of petrol vehicles on the road are compatible, including every new car built since 2011. E10 has been the standard grade in Great Britain since September 2021, and in Northern Ireland since November 2022.
Vehicles that may not be compatible include:
- classic and cherished cars
- some specific models from the early 2000s (the RAC suggests caution with cars registered before 2002)
- some mopeds of 50cc or under
- boats, and petrol garden tools such as lawnmowers and chainsaws
To be sure, use the government's free E10 vehicle checker. You'll need the make, model and year.
I put E10 in a car that can't take it. What now?
Don't panic. According to government guidance, a single tank of E10 in a non-compatible vehicle "should not be a major problem". Fill up with E5 next time. Unlike putting petrol in a diesel car, you shouldn't need to drain the tank. The risk comes from using E10 over a long period, which can damage seals, plastics and metal parts in older fuel systems.
Does E10 mean worse fuel economy?
Slightly. The government puts it at around 1%, which it says is "unlikely to be noticeable in everyday driving". On a car doing 40 miles per gallon, that's roughly 0.4 mpg.
That is far less than the price gap between the two grades. With unleaded at around 175p a litre, E5 at 12p more and E10 using about 1% more fuel, E10 still works out around 5% cheaper per mile.
Is super unleaded better for my car?
For a normal car designed to run on 95 octane, there's usually no real benefit. The RAC says most drivers are unlikely to see any efficiency gain, and Which? puts the premium at 10p to 15p a litre for "usually little benefit".
Higher-octane fuel can make sense if:
- your handbook or fuel filler cap says the car needs 97 or 98 octane (common on high-performance engines)
- your car isn't E10-compatible, in which case E5 is the safe choice
Cars and tools that sit unused
Ethanol absorbs water from the air. In a car that's laid up for months, or a lawnmower stored over winter, that can lead to condensation and corrosion in the fuel system. If you store a classic car, the historic vehicle clubs' federation (FBHVC) recommends ethanol-free petrol. For garden equipment, the usual advice is to run the tank dry or drain it before storing it for more than about a month.
What about diesel?
Standard diesel is labelled B7, meaning it contains up to 7% biodiesel, and it works in all diesel cars. There's no cheaper or dearer "eco" grade to choose between in the same way, but prices still vary a lot between forecourts. As of 2 October 2026, the RAC reported the UK average for diesel at a record 200.01p a litre.
Why did the UK switch to E10?
Ethanol is made from crops, so it releases less fossil carbon than petrol. The government estimated that E10 could cut transport CO2 emissions by 750,000 tonnes a year, which it compared to taking 350,000 cars off the road.
The bottom line
- If your car is compatible (almost certainly, if it's newer than 2011), buy E10. It's the cheaper grade, and the economy difference is tiny.
- Only pay for E5 super unleaded if your car isn't E10-compatible or your handbook asks for higher octane.
- Whatever you buy, the forecourt you choose matters more than the grade: prices for the same fuel can differ by several pence a litre within a few miles.
PlugOrPump shows live E10 and diesel prices for every forecourt near you, cheapest first. Search by postcode or browse fuel prices by town.