What is E10 petrol?

From September 2021, fuel stations across the UK started selling a new type of petrol called E10. It replaced E5 petrol as the ‘standard’ petrol at all fuel stations, although E5 is often still available as premium unleaded. But why the change and what does it mean for your car? Here’s our handy guide to E10 petrol.

Petrol is mostly made from oil but there’s a percentage of ethanol (pure alcohol, essentially) in it, too. The regular 95 octane petrol that currently comes out of the green pump at a fuel station is known as E5. That means 5% of it is ethanol. The new E10 petrol is 10% ethanol. 

The main difference between E5 and E10 is the percentage of ethanol used. Using more ethanol and less oil-based petrol reduces CO2 exhaust emissions, and also reduces the dependence on fossil fuels.

The growing climate change crisis is spurring governments in many countries to use as many means as possible to reduce carbon dioxide emissions. Switching to E10 petrol helps achieve that goal because cars produce less CO2 when they burn ethanol in their engines. According to the UK government, switching to E10 could reduce total CO2 emissions from cars by up to 2%. Not a huge difference, but every little helps.

You can still buy E5 petrol, as premium-grade petrol remains as E5. However, it will cost more than standard petrol, which is now E10.

Petrol is a fossil fuel mostly made from crude oil, but the ethanol element is made from plants. Most of the companies that make fuel use ethanol that’s produced as a byproduct of sugar fermentation, primarily in breweries. That means it’s renewable and therefore much more sustainable than oil, reducing CO2 emissions during its  production as well as when it’s being used.

Most petrol-powered cars in the UK can use E10 fuel, including all petrol cars sold new since 2011 and many made between 2000 and 2010. Even at the 10% formula, the UK actually uses quite a low percentage of ethanol compared to some other countries that have used much more for many years. There are even some countries where cars use pure ethanol. Most cars available in the UK are sold worldwide, so they’re designed to use petrol with a greater ethanol content.

Most cars made since 2000 can use E10 fuel, but that’s only a rough guide. You need to know for sure whether your car can use it. (Doing so could damage your car’s engine – see ‘What can happen if I use E10 fuel by mistake?’ below.)

Fortunately, the UK government has a website where you can select the make of your car to check whether it can use E10 fuel. In many cases, the vast majority of models can use E10, but any exceptions are clearly listed.

Only regular, 95 octane petrol from the green pump will now be E10. High-octane premium petrol like Shell V-Power and BP Ultimate will continue to be E5, so if your car can’t use E10 you can still top up using this. Unfortunately, premium fuel will cost you around 10p per litre more than regular petrol, but your car’s engine should run better and might even give you better fuel economy. Premium petrol is usually dispensed from a green pump that’s branded with either the fuel’s name or the octane rating of 97 or higher.

Using E10 petrol in a car that’s not designed for it won’t cause any issues if you fill up with it just once or twice. If you do so by accident you won’t need to get the fuel tank flushed out but it’s a good idea to add some E5 petrol as soon as you can to dilute it. It’s fine to mix the two. 

If you use E10 repeatedly in a car that’s not designed for it, the fuel can start to erode some of the engine components and cause long-term (and potentially very costly) damage.

If your car can run E10 then it’s no problem at all to run a mix of E10 and E5.

Fuel economy can be slightly worse when the ethanol content in petrol increases, so you may notice a small decrease in how far you can go on a fuel tank. Independent tests by a consumer motoring magazine suggest that those using E10 will see fuel economy drop by between 6% and 11%, with cars using smaller engines affected the most.

The introduction of E10 petrol coincided with steep rises in petrol prices, which makes it hard to make a direct cost comparison between E10 and E5. 

The price difference between standard grade and premium petrol hasn’t changed much, however, so it’s fairly safe to say that, like-for-like, E10 petrol costs about the same as its predecessor.

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