What is E10 fuel and how will it affect you?

The previous standard petrol graded in the UK contained up to 5% bioethanol, known as E5. E10 fuel increases the share of the renewable energy produced using crops to 10%.

It’s estimated by the government that the greener fuel could reduce CO2 emissions by 750,000 tonnes per year, the equivalent of taking up to 350,000 cars off the road.

Estimates fail to mention, however, that around 600,000 vehicles on our roads aren’t compatible with the fuel.

Here is a look at the pros and cons of using this fuel as a genuine answer to the problem of increasing emissions. 

E10 is a biofuel made up of 90% regular unleaded and 10% ethanol – hence the E10 name.

The standard unleaded fuel used until E10's introduction contained up to 5% ethanol and could be used in any petrol-engined car without problems or the need for modification. That's now become the standard for super unleaded, which older cars can use instead.

With E10, things aren’t quite so simple, which is why its roll-out in the UK compared to other European countries was delayed.

Ethanol is an alcohol-based fuel produced from the fermentation of a range of plants, including sugar cane and grains, along with their byproducts.

Unlike regular unleaded petrol, ethanol fuel is said to be partially atmospherically carbon-neutral. This is because as the plants that will become biofuel grow, they reportedly absorb more carbon dioxide than what will be released into the air during fuel production and combustion¹.

This partially offsets the greenhouse gas emissions produced by its production and use, but by just how much is still an active topic of debate.

In short, no. Its estimated that 3% of vehicles - as many as 600,000 - on our roads aren't compatible with E10 - you can see if your car is compatible with the fuel by using the government's E10 online checker.

Drivers are advised to contact car manufacturers with any questions surrounding their specific vehicle. For example, Vauxhall says “E10 fuel can be used in all petrol-engine Vauxhall vehicles except models with the 2.2-litre direct-injection petrol engine (code Z22YH) used in Vectra, Signum and Zafira.”

As a rule, drivers of cars registered prior to 2002 are advised not to use E10 in their vehicle, as problems have been reported. These cars can instead fill up with high-octane super unleaded, which is still E5. As of 2011, all new cars sold in the UK must be E10 compatible.

If you put E10 fuel in an incompatible car it will still run, but seals, plastics and metals may be damaged over longer periods as a result of bioethanol's corrosive properties. It is a hygroscopic, which means it absorbs water from the atmosphere, leading to condensation in fuel tanks if the car remains unused for long periods of time.

RAC fuel spokesman Simon Williams said: “those with E10 compatible cars will unfortunately find they are getting fewer miles to the gallon as the fuel is less efficient than E5 fuel, due to it containing 5% more ethanol.

“Owners of classic cars need to be particularly careful not to accidentally fill up with E10 and then leave it sat in the tank for long periods, as this will likely lead to expensive damaged seals, plastics and metals.

“But people who fill up a non-compliant car with E10 don’t need to panic. They shouldn’t suffer any lasting damage to their vehicle as long as they put the correct fuel in as soon as possible – when around a third to half the tank is used. While using up the fuel they may, however, experience a little poor cold starting and rough running.”

The consequence of putting E10 fuel in an incompatible vehicle depends on the vehicle/engine variant and how much fuel has been put in.

It may cause some pre-detonation (‘pinking’), and perhaps a little rough running and poor cold starting, but it shouldn't be a disaster for the driver.

Simply top up with the correct fuel suitable for the vehicle as soon as possible when around a third to half the tank is used.

Although RAC Breakdown Cover members have access to a discounted Fuel Drain Patrol service, a drain shouldn't be necessary unless in the highly unlikely event that the engine would not run at all.

This depends on who you speak to. Environmental groups will point to carbon-offsetting properties, while the government has introduced E10 as a step towards meeting its emissions targets.

But E10 is less efficient than the current E5 blend of fuel, with the problem exacerbated in smaller-engined cars.

RAC fuel spokesman Simon Williams said: “those drivers who have no choice but to use super unleaded E5 petrol will be paying through the nose, as it's more expensive than the current UK average for standard unleaded.

“This will quickly mount up for anyone who has to drive a lot of miles to get to work every week. It’s also probably the case that many of those driving older cars will already be from lower income backgrounds, so they will end up being even worse off.

“And those with E10 compatible cars will unfortunately find they are getting fewer miles to the gallon as the fuel is less efficient than E5 fuel, due to it containing 5% more ethanol.

The US Energy Information Administration (EIA) claims the energy content of ethanol is about 33% less than pure unleaded and that "the impact of fuel ethanol on vehicle fuel economy varies depending on the amount of denaturant that is added to the ethanol."²

The EIA states: “The energy content of denaturant is about equal to the energy content of pure gasoline (petrol). In general, vehicle fuel economy may decrease by about 3% when using E10".

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Reacting in 2019 to proposals to introduce E10 petrol in the UK, RAC fuel spokesman Simon Williams said:

“Everybody agrees that steps must be taken to reduce emissions from road transport, however introducing E10 as the standard petrol will pose some challenges. 

"Firstly, as the RAC Foundation points out, there could be as many as 600,000 vehicles on our roads that aren’t compatible with the fuel.

"Many of these are likely to be owned by those from lower income backgrounds and while it is welcome that E5 petrol is not being phased out altogether, owners of these vehicles will face higher fuel costs – and will also have to hunt out those forecourts that still sell E5.

"Some retailers will also not have the capacity to be able to provide both E5 and E10 fuels on forecourts, so the impact is likely to be most keenly felt by those with incompatible vehicles in rural areas.

"It is also vital that owners of affected vehicles are aware of the changes. We’d like to see the DVLA writing to these owners to inform them that E5 will no longer be the standard premium grade, and to let them know their options.

"This, alongside a trusted online resource where drivers can quickly identify if their vehicles are E10 compatible or not, will go a long way to avoiding any expensive problems from filling up wrongly with the new blend.

"For the overwhelming majority of drivers with compatible vehicles, the introduction of E10 petrol will make little difference other than a possible slight reduction in fuel economy."

Drivers of older, incompatible cars may have to shell out for more expensive fuel, since forecourts still only offer E5 as a premium option.

Thankfully, an online resource has since been published. You can find the government’s E10 fuel compatibility checker here.

It’s estimated that the greener fuel could reduce CO2 emissions by 750,000 tonnes per year, the equivalent of taking up to 350,000 cars off the road in the UK.

The E10 blend was already used in other countries such as Belgium, Finland, France and Germany before it was introduced in the UK. 

Robin Wright, secretary general of environmental campaign groups ePURE, said: “Displacing 10% of Europe’s petrol with ethanol through E10 fuel, a fuel widely available in France, Finland and Germany, would reduce greenhouse gas emissions from petrol vehicles by over 6%.

“But more ambition and greater use of ethanol is needed. Brazil currently mixes its petrol with up to 28% ethanol, so why not Europe?”

Finland is leading the way in Europe. E10 fuel has increased its share of petrol sold each year since it was introduced at the beginning of 2011, with the Finnish Petroleum and Biofuels Association reporting a 63% share in 2015.

E10 petrol fully rolled out in late 2021. This news story carries full details.