E10 vs E5 Petrol Explained: Which Should You Use?
In September 2021, the UK switched its standard petrol from E5 to E10. But what exactly is E10, is your car compatible, and do you need to buy more expensive Super Unleaded instead?
E10 vs E5 at a Glance
| Feature | E10 (Standard Unleaded) | E5 (Super Unleaded) |
|---|---|---|
| Ethanol content | Up to 10% | Up to 5% |
| Octane rating | 95 RON | 97–99 RON |
| UK pump colour | Green | Blue |
| Fuel economy | Baseline | ~1–3% better |
| Price | Cheaper (standard) | 10–20p/litre more |
| Availability | All petrol stations | Most stations |
| Car compatibility | Post-2002 mostly | All petrol cars |
| CO2 emissions | Slightly lower | Slightly higher |
What is E10 Petrol?
E10 is the name for standard unleaded petrol (95 RON) blended with up to 10% bioethanol. Bioethanol is a renewable alcohol fuel made by fermenting crops such as wheat, sugar beet, and corn. The UK government mandated the switch from E5 to E10 as the standard grade in England, Scotland and Wales in September 2021 (Northern Ireland followed in November 2022).
At the pump, E10 is dispensed from the green nozzle. It's the cheapest grade of petrol and what most UK drivers should use unless their car is incompatible.
What is E5 Super Unleaded?
E5 is petrol containing up to 5% ethanol. Before September 2021, E5 was the standard unleaded grade. Now, E5 is sold only as "Super Unleaded" — the premium, higher-octane grade (97–99 RON). At the pump it comes from the blue nozzle.
Super Unleaded is typically 10–20p per litre more expensive than standard E10. The higher octane rating means it can offer slightly better performance and fuel economy in high-compression or turbocharged engines — but for most everyday cars, the extra cost isn't justified.
Is Your Car Compatible with E10?
The vast majority of petrol cars are E10 compatible. As a general rule:
- ✓All petrol cars made from 2011 onwards are E10 compatible by EU/UK law
- ✓Most petrol cars made between 2002 and 2010 are compatible
- !Some pre-2002 cars, motorcycles, and small engines may not be compatible
- ✗Classic cars, older motorcycles, and some older models should use E5
Does E10 Affect Fuel Economy?
Ethanol contains approximately 34% less energy per litre than petrol. Because E10 contains up to 10% ethanol, it has slightly less energy content than the old E5 blend. In practice, this translates to approximately 1–3% worse fuel economy — around 0.5 to 1 mpg worse for most cars.
On a car averaging 45 mpg over 10,000 miles a year, the difference amounts to roughly £15–£40 more spent on fuel annually. Since E10 is significantly cheaper per litre than Super Unleaded E5, switching to E5 to recover that fuel economy loss doesn't make financial sense for compatible cars.
When Should You Use E5 Super Unleaded?
- 1Your car is not E10 compatible — check the gov.uk compatibility checker and always use E5 if your vehicle is listed as incompatible.
- 2You own a classic car or older motorcycle — older rubber seals and fuel system components can be damaged by higher ethanol concentrations over time.
- 3You have a high-performance car with a high-compression engine — some sports cars benefit from 97+ RON fuel. Check your owner's manual.
- 4Your manufacturer specifically recommends 97+ RON — a small number of premium manufacturers require Super Unleaded for warranty compliance.
E10 vs E5 FAQ
What is E10 petrol?
E10 is a type of unleaded petrol that contains up to 10% renewable ethanol blended with 90% regular petrol. The "E" stands for ethanol and "10" refers to the percentage. It has been the UK standard (95 RON) unleaded petrol since September 2021, replacing the previous E5 standard blend.
What is E5 petrol (Super Unleaded)?
E5 petrol contains up to 5% ethanol. In the UK, E5 is now sold as "Super Unleaded" (97+ RON) and is the grade to use if your car is not compatible with E10. Super Unleaded typically costs 10–20p per litre more than standard E10.
Is my car compatible with E10?
Most petrol cars made after 2002 are compatible with E10. All new petrol cars sold in the UK since 2011 must be E10 compatible. You can check your car using the government's free E10 compatibility checker at gov.uk. If in doubt, use E5 Super Unleaded.
Does E10 reduce fuel economy?
Yes, slightly. Ethanol contains less energy per litre than petrol, so E10 gives approximately 1–3% worse fuel economy than the old E5 standard blend. In practice, this is around 0.5–1 miles per gallon difference, so the cost difference per mile is negligible compared to the price gap between forecourts.
Can I mix E10 and E5 in my tank?
Yes, mixing E10 and E5 is safe and won't damage your fuel system. If your car is E10 compatible, you can top up with E5 without any issues. If your car is NOT E10 compatible, you should use E5 (Super Unleaded) exclusively, though occasional mixing won't cause immediate damage — just switch to E5 as soon as possible.
What happens if I put E10 in a car that's not compatible?
Using E10 in an incompatible car over time can cause damage to fuel system components such as rubber seals, gaskets, fuel lines, and some metal parts. Short-term use is unlikely to cause immediate damage, but persistent use may lead to fuel leaks, rough running, and corrosion in older fuel systems. Switch to E5 immediately if you discover your car is incompatible.
Why did the UK switch to E10 petrol?
The UK government switched the standard petrol grade to E10 to reduce carbon dioxide emissions from road transport. Bioethanol is produced from crops and is considered a renewable fuel. Switching from E5 to E10 is estimated to cut CO2 emissions equivalent to taking 350,000 cars off the road annually.
Is E10 cheaper than E5 Super Unleaded?
Yes. E10 (standard unleaded) is typically 10–20p per litre cheaper than E5 Super Unleaded. Over a full 55-litre tank, that's £5.50–£11 more for Super Unleaded. Unless your car requires E5, E10 is the economical choice despite its very slight fuel economy disadvantage.
Find the Cheapest E10 or Super Unleaded Near You
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