E10 Fuel Guide

Published 1 October 2026 · Updated 22 October 2026

E10 petrol — the blend of 10% bioethanol and 90% conventional petrol — is now the standard grade petrol across the UK, EU, Australia, and many other markets. The switch from E5 (5% ethanol) to E10 was one of the most significant changes to forecourt fuel in decades, generating widespread consumer questions about vehicle compatibility, fuel economy impact, and whether it actually helps the environment. This guide answers them.

For how petrol taxes shape the pump price you pay for E10, see our price at the pump guide. For the E85 high-ethanol blend used in flex-fuel vehicles, see our E85 glossary entry. For sustainable aviation fuel — the aviation equivalent — see our SAF 2026 analysis.

What is E10 petrol?

E10 is a blend of up to 10% bioethanol (fermented from biological feedstocks — wheat, sugar beet, corn, or agricultural residues) and 90% conventional unleaded petrol. It replaced E5 (5% ethanol blend) as the standard petrol grade in most Western markets:

• UK: E10 became the standard petrol grade in September 2021; E5 97+ octane (Super Unleaded) retained as a protection grade
• EU: E10 became the minimum standard across all EU member states from January 2024 under the Fuel Quality Directive revision
• Australia: E10 available but not mandatory standard; E5 still dominates in most states
• USA: E10 has been the standard since ~2011; the US moved from E0 to E10 earlier than Europe; E15 approved in more markets
• Brazil: E27 (27% ethanol blend) is the standard — the world's highest mandatory ethanol blend due to Brazil's large sugarcane-based ethanol industry

Vehicle compatibility

If your vehicle is incompatible with E10, you should use E5 Super Unleaded (typically 97+ octane, labelled as Super Unleaded or 99 at the forecourt). E5 is retained as a protection grade in the UK and available at most large filling stations. It is more expensive (typically 10–20p/litre premium in the UK).

Fuel economy impact of E10

E10 delivers slightly fewer miles per gallon than E5 due to ethanol's lower energy density:

• Ethanol energy density: ~21.2 MJ/litre
• Petrol energy density: ~32 MJ/litre
• E10 energy density: ~31 MJ/litre (approximately 3% lower than E5)
• Real-world MPG reduction: approximately 1–2% for modern vehicles with adaptive ECUs; up to 3% for older or less adaptive engines
• Example: a car achieving 50 mpg on E5 would achieve approximately 49–49.5 mpg on E10

The financial impact is minor — at £1.50/litre petrol price, a 2% MPG reduction costs approximately £3 per 100 litres consumed. However, if E10 is priced identically to E5 at the pump (as is common in the UK), the effective cost per mile increases marginally. For current petrol prices in major markets, see our global petrol price comparison guide.

E10 vs E5 Super Unleaded — which should you choose?

The environmental case for E10

The shift from E5 to E10 is estimated to reduce carbon emissions from UK road transport by approximately 750,000 tonnes of CO2 equivalent per year — equivalent to removing 350,000 cars from the road. This assumes:

• Ethanol feedstocks (wheat, sugar beet) absorb CO2 as they grow — so the carbon released when burning ethanol is partially offset by biogenic absorption
• UK wheat-derived ethanol has approximately 65–70% lower lifecycle CO2 than petrol (accounting for farming, transport, and processing)
• Doubts: indirect land use change (ILUC) — if biofuel crops displace food production, land cleared elsewhere may emit CO2; UK wheat ethanol generally has lower ILUC risk than imported biofuels

Bioethanol and the future of ethanol blended petrol

Understanding what is E10 petrol requires context on what is bioethanol — the renewable alcohol produced by fermenting plant sugars from crops like wheat, corn, and sugar beet. Bioethanol is blended into petrol to reduce lifecycle carbon emissions: because the crops absorb CO₂ as they grow, the carbon released during combustion is partially offset by this biogenic absorption cycle. The comparison of E5 vs E10 petrol comes down to ethanol content (5% vs 10%) and its effects on energy density and compatibility. E10 has approximately 3% less energy per litre than E5, resulting in a marginal fuel economy reduction of 1–2% for most modern vehicles. The IEA's bioenergy tracker monitors global ethanol production capacity, which has grown significantly as E10 mandates have spread across Europe and beyond.

E10 fuel compatibility remains the top concern for drivers of older vehicles. The UK government's E10 compatibility checker allows owners to verify by make, model, and year whether their vehicle can safely use ethanol blended petrol. The primary risk is that ethanol acts as a solvent and hygroscopic agent — it can degrade older rubber seals, corrode certain metals, and absorb water from the atmosphere, leading to phase separation in fuel tanks that sit unused for extended periods. For compatible modern vehicles (2002 onwards), E10 is entirely safe and no different in everyday use from the E5 it replaced. The European Commission's renewable energy directive mandates increasing biofuel blending levels, meaning E10 is likely the beginning of a broader shift — E15 and E20 blends are already under discussion for future European fuel standards, and Brazil already operates at E27 as standard.