The Difference Between E5 and E10 Petrol | MICHELIN Connected Fleet

The difference between E5 and E10 petrol is the amount of renewable ethanol blended into it. E5 contains up to 5% ethanol; E10 contains up to 10%. Since September 2021, E10 has been the UK's standard unleaded grade, while E5 is sold as the pricier "super unleaded". E10 lowers CO2 emissions but is slightly less fuel-efficient and isn't suitable for some older vehicles.

Given the tightening of environmental regulations, fleet managers are under constant pressure to reduce carbon emissions for ESG compliance. The introduction of E10 petrol in 2021 added a new layer of complexity around operating costs and vehicle performance. This guide explains what E10 petrol is, how it differs from E5, and what the change means for fleets.

Quick facts: E5 vs E10 petrol

• E5 = up to 5% renewable ethanol; now sold as super unleaded (typically 97-99 RON).
  
  
• E10 = up to 10% renewable ethanol; the standard unleaded grade at UK pumps (95 RON).
  
  
• Rollout: E10 became standard in Great Britain on 1 September 2021, and in Northern Ireland in November 2022 (Fuels Industry UK).
  
  
• Emissions: E10 could cut UK transport CO2 by around 750,000 tonnes a year, the equivalent of taking roughly 350,000 cars off the road (Department for Transport).
  
  
• Compatibility: About 95% of petrol vehicles on UK roads can use E10, and all petrol cars built since 2011 are approved for it. An estimated 600,000-700,000 older vehicles are not compatible (Zemo Partnership / DfT).
  
  
• Efficiency: The DfT estimates E10 reduces fuel economy by around 1% versus E5.
  
  
• Price: E5 super unleaded typically costs 10-15p more per litre than E10 (UK consumer fuel-price comparisons, 2026).

What is E10 petrol?

E10 petrol is unleaded fuel blended with up to 10% renewable ethanol and 90% petrol. The "E" stands for ethanol and the "10" for the maximum percentage.

E10 is the UK's standard unleaded fuel, introduced to replace E5 at most stations. By raising the bioethanol content from 5% to 10%, E10 reduces reliance on fossil fuels and lowers overall CO2 emissions. Its use is mandated under the UK's Renewable Transport Fuel Obligation (RTFO), and it has been the reference fuel for new-car emissions and performance testing since 2016. This makes E10 a key part of the Government's strategy to cut greenhouse gas emissions from the transport sector and progress towards net zero.

What is E5 petrol?

E5 petrol is unleaded fuel containing up to 5% renewable ethanol. Before September 2021 it was the UK's standard grade; it is now sold almost exclusively as high-octane "super unleaded".

E5 is now positioned as a premium product. Because it is typically a higher-octane fuel (around 97-99 RON, versus 95 RON for E10), it offers better resistance to engine knock and marginally better fuel efficiency in high-performance or older engines. It remains widely available as the "super unleaded" grade and is the recommended fuel for vehicles that are not E10-compatible.

What is the difference between E5 and E10 petrol?

The headline difference is ethanol content, but that single change affects cost, compatibility, emissions and efficiency:

Is E5 or E10 better, and which should you use?

For most modern petrol vehicles, E10 is the better everyday choice. It's cheaper and lower-carbon, and the small efficiency loss rarely outweighs the price saving. Use E5 if your vehicle is older or pre-2011, is a classic, or its handbook specifies a higher octane.

Use this quick guide:

• Choose E10 if your vehicle was built in 2011 or later and the manufacturer approves it (the vast majority of cars). It costs less and lowers your fleet's carbon footprint.
  
  
• Choose E5 if your vehicle is pre-2011, a classic, a motorcycle/moped with an older engine, or is used infrequently (ethanol attracts moisture during long storage). E5 is also worth it where a handbook specifies 97+ RON.
  
  
• If in doubt, check before filling as using E10 in an incompatible engine over time can damage seals, gaskets and fuel lines.

Is E10 petrol compatible with my vehicle?

Around 95% of petrol vehicles on UK roads are compatible with E10, and all petrol cars built since 2011 are approved for it. However, an estimated 600,000-700,000 vehicles are not.

Vehicles that should usually stick to E5 super unleaded include:

• Classic and vintage cars, particularly pre-2001 models or those with carburettors
• Some models built between 2000 and 2011 with ethanol-sensitive seals or fuel lines
• Older motorcycles and mopeds, especially some two-stroke engines
• Garden equipment and small engines (lawnmowers, etc.)

You can confirm compatibility for any vehicle using the Government's free checker at gov.uk/check-vehicle-e10-petrol.

Does E10 reduce fuel economy?

Slightly. The Department for Transport estimates E10 reduces fuel economy by around 1% compared with E5, because ethanol holds less energy per litre than petrol. Many drivers report a real-world drop of 1-2%.

For most drivers this is barely noticeable and is far smaller than the effect of driving style or under-inflated tyres. For large or high-mileage fleets, however, even a 1% efficiency loss accumulates into a meaningful cost over thousands of vehicles and miles, which is why ongoing monitoring matters.

How does switching from E5 to E10 affect fleets?

Moving from E5 to E10 isn't just a matter of refilling with a new fuel. Fleet managers should plan around three areas:

1. Cost control. E10 is cheaper per litre, but its slightly lower efficiency offsets some of the saving. Across a large fleet, small per-litre and per-mile differences add up, so fuel consumption needs continued tracking to protect the gains from route optimisation.
   
   
2. Vehicle maintenance. Ethanol is more corrosive than pure petrol. In engines not built for higher ethanol levels, prolonged E10 use can degrade seals, clog filters and injectors, and cause leaks, rough idling or hard starting. Confirm compatibility for every vehicle, as incompatible (often older) vehicles drive up maintenance costs and downtime.
   
   
3. International operations. The E10 rollout isn't uniform worldwide. Many European countries have adopted it, but some have not made it available nationwide, which affects refuelling logistics, route planning and vehicle compatibility when operating across borders.

Help your fleet adapt to E10 fuel

The transition to E10 supports fleet sustainability, but adapting well takes planning: reviewing vehicle compatibility, monitoring fuel consumption, and adjusting operations to maintain efficiency.

At MICHELIN Connected Fleet, our fleet management solutions and expert consultancy help you anticipate these challenges, control fuel expenses, and avoid costly disruptions. If you’re interested, then be sure to make an enquiry into our services today.

FAQs

What does the "E" in E5 and E10 mean?

It stands for ethanol. The number is the maximum percentage of renewable ethanol in the fuel, so 5% for E5, 10% for E10.

Is E10 bad for my car?

Not if your vehicle is E10-compatible (all petrol cars from 2011 onward, and around 95% of the fleet). In incompatible older engines, long-term use can damage fuel-system components.

Can I mix E5 and E10?

Yes. If your vehicle is E10-compatible, mixing the two grades in any ratio is safe.

Why is E5 more expensive now?

E5 is sold as premium "super unleaded", a higher-octane fuel that costs more to produce, typically 10-15p more per litre than standard E10.

Is E10 available across Europe?

In many countries, yes, but availability isn't universal, which is an important consideration for cross-border fleet operations.