Since September 2021, the standard unleaded petrol at UK pumps changed from E5 to E10. If you've wondered what the numbers mean, whether your car is compatible, and if super unleaded is worth the premium — this guide covers everything.
The "E" stands for ethanol, and the number is the maximum percentage of ethanol blended into the petrol. E10 contains up to 10% ethanol, while E5 contains up to 5%.
Ethanol is a renewable biofuel made from crops like sugar beet and wheat. The UK government introduced E10 as the standard petrol to help reduce CO2 emissions — the higher ethanol content is estimated to cut transport CO2 by 750,000 tonnes per year, equivalent to taking 350,000 cars off the road.
| E10 (Unleaded) | E5 (Super Unleaded) | |
|---|---|---|
| Ethanol content | Up to 10% | Up to 5% |
| Octane rating | 95 RON | 97-99 RON |
| Typical price | ~130p/litre | ~143p/litre |
| Car compatibility | Most cars from 2011+ | All petrol cars |
| Energy content | Slightly lower | Slightly higher |
| Availability | Every UK station | Most UK stations |
Almost all petrol cars manufactured from 2011 onwards are fully compatible with E10. Many older cars are too. The government provides an online checker at gov.uk/check-vehicle-e10-petrol.
Cars that may not be compatible include some models made before 2002, certain classic cars, and a few specific models from the early 2000s. If your car isn't E10 compatible, you should use E5 (super unleaded) instead.
What happens if I accidentally put E10 in an incompatible car? Don't panic. A single tank won't cause immediate damage. However, prolonged use can corrode certain seals, gaskets, and metal components in the fuel system. If you realise the mistake, fill up with E5 next time.
Yes, slightly. Ethanol contains less energy per litre than pure petrol. In practice, E10 typically gives 1-2% lower fuel economy compared to E5. On a 55-litre tank that gets 40mpg, that's roughly 5-10 fewer miles per tank.
However, the price difference between E10 and E5 is usually 10-15p per litre. Even accounting for the slight mpg drop, E10 is significantly cheaper overall.
For most drivers, no. The higher octane rating (97-99 RON vs 95 RON) only benefits cars with high-compression or turbocharged engines that are specifically tuned for it. Your car's manual will tell you if premium fuel is recommended.
The main reasons to use E5 super unleaded:
If none of these apply, save your money and stick with E10.
For the vast majority of UK drivers, E10 is the right choice. It's cheaper, widely available, and your car almost certainly runs fine on it. Use Tanki to find the cheapest E10 near you and save even more.
If you need E5, Tanki shows super unleaded prices too — just tap "Super (E5)" to compare.
Compare E10 and E5 prices near you
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