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E10 petrol is coming to the UK – will it affect you and your vehicle?

is e10 petrol or diesel
Martynn Randall Haynes manuals

Martynn Randall is technical editor at Haynes and has been with us for 27 years. He's written more than 60 Haynes publications and has owned more than 85 cars and 60 motorbikes... so far!

From September 2021, the UK government will allow the introduction of E10 petrol at filling stations. ‘E10’ is a reference to the percentage of ethanol mixed into the petrol. Currently, the UK's normal ‘baseline’ petrol is E5. It contains 5% ethanol, so E10 contains twice the amount.

The government claims that CO2 production will be cut by as much as 750,000 tonnes annually as a result of this change, but there could be some negative effects, too.

What is E10 and will it work in my car?

If your vehicle is less than 20 years old and is driven regularly (at least once a week), you're unlikely to notice any differences when using E10 petrol. But if your vehicle is left unused for a couple of weeks or more, the water content in the fuel will rise because ethanol absorbs water. This could cause corrosion in the fuel system and poor starting and performance.

What is ethanol?

Ethanol is ethyl alcohol, a plant-based biofuel made from biomass such as corn or sugar cane. Being plant-based, it’s a renewable form of fuel, not a fossil fuel.

Ethanol is a solvent

Ethanol will slowly eat through rubber, plastic and fibreglass. This will affect rubber seals and hoses in the fuel systems of older vehicles in particular, causing the material to perish and eventually leak. One solution is to replace them with special ethanol-proof components (fuel hose, seals, etc.). Ethanol is particularly bad news for solder, so older vehicles with carburettors and brass floats will be especially vulnerable.

Ethanol is 34% less energy-dense than petrol

So to get the same power output from your engine, that accelerator pedal is going to have to be pressed harder! Obviously, this will have an effect on your vehicle's fuel consumption.

Will my vehicle be affected?

The government claims there are currently around 600,000 vehicles on the road in the UK that should avoid using E10. Generally speaking, if your vehicle was made after 2000, it should be okay. Check here.

What should I do if my vehicle can’t use E10?

The good news is that the government has promised that E5 fuel will be available for at least five years. 
The not so good news is that only filling stations that sell more than 1,000,000 litres of fuel in total will need to ensure one of the fuels on offer is E5 (with some exceptions). You can be sure that, where available, E5 prices will rise accordingly.


where can i buy e10?

Vehicles in storage

Fuel left in the tank for weeks will begin to degrade. The ethanol will absorb more moisture from condensation, and begin to separate out from the petrol it was mixed with. This will cause corrosion in metal fuel system components and could cause other problems.

Certain types of plastic and fibreglass ‘swell’ when exposed to ethanol. Plastic fuel tanks seem especially affected by this, with mountings no longer aligning and sender unit caps no longer fitting. 

One possible solution is an additive that, when combined with the fuel, stabilises the ethanol, preventing it from separating out and helping to prevent corrosion. There are many suitable additives available, such as Millers Ethanol protection or Lucas Oil Ethanol fuel conditioner. Check with your owner's club or the Federation of British Historical Vehicle Clubs.

So is ethanol in fuel a good idea?

Given the problems it causes for older vehicles, the increase in fuel consumption and the increasing amount of land now used for fuel production that used to grow food, the jury’s still out on this one.

Final thought

Almost 85% of biomass used for ethanol production is grown in the United States (65%) and Brazil (23%). Cash is king…