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E10 Fuel: Eco Triumph or Fuel Economy Disaster?

February 14, 2014

Fuel. We all need it and, sadly, there’s no getting away from the fact that our current favourite, petrol, will one day run out. Many alternatives have been suggested − electricity, hydrogen, biodiesel. All have their merits, but all also have their disadvantages. Not least of which is that, for petrol-users, they all require us to buy new cars.

But what if there were a way for us to keep our current cars, keep burning petrol, but find a way to make the finite supplies we’ve got go just a little bit further? Enter the world of petro-ethanol blends, otherwise known as ‘gasahols’.


Ethanol can be blended with petrol in a variety of ratios (or even used neat), but for use in a standard petrol engine a blend of 10% ethanol and 90% petrol is most common. Fuel using this ratio is known as E10 and, although it’s been used around the world for some years, it’s now finally making its way into Britain. But is that something to celebrate, or greet with a wary caution?

The advantages of switching to an ethanol-petrol blend are obvious, so obvious that countries such as Thailand have already switched over to exclusively using E10 in place of high octane petrol. Not only can petrol-ethanol blends help stretch out the world’s dwindling supply of fossil fuels, but the ethanol used can be produced from biofuels – making this not just a renewable source of energy, but also helping to reduce the fuel’s overall carbon footprint thanks to the CO2 absorbed through growing the biofuel crops.

It’s also worth noting that, although price fluctuations mean that, currently, bioethanol is sometimes cheaper and sometimes more expensive than petrol – in the long term, petrol is likely to get significantly more expensive, thus reducing the relative cost of bio-ethanol.

E10 and its ilk have the potential to reduce the net CO2 entering the atmosphere, allow us to keep running our petrol-reliant cars for longer and, in the long term, possibly even save us money.

There are, however, some not insignificant disadvantages to gasahols that call their “miracle fuel” status into question.

Firstly, while any car built after the early nineties should be able to run off E10 (and more petrol heavy blends) just fine, older cars – or those wanting to use fuel blends with a greater percentage of ethanol (such as E15 or E25) – will need their engines modified to provide a higher compression ratio.

Secondly, even modern cars using low ethanol blends like E10 will tend to suffer from issues such as metal corrosion and degradation of rubber and plastic components, due to the reactive nature of ethanol. This means parts will need to be replaced on a much more regular basis, significantly reducing any potential economic advantages.

Thirdly, and perhaps most significantly, ethanol-petrol blends have been found to give much worse mileage than conventional fuels, with What Car? recently finding that E10 fuel was a staggering 8.4 percent less efficient than pure petrol. They calculated that this would work out to over two extra full tanks of petrol per year for a standard car, at a cost of £170 (assuming both fuels cost the same).

This not only has an economic impact for ethanol-petrol blends, but, thanks to the greater amount of E10 being consumed per mile compared to petrol, the cars running the blended fuel actually ended up producing more CO2 overall than those using standard fuel.

So, while E10 fuel may help us eke out of beloved petrol for a few extra years, it is currently neither cheaper, nor necessarily more environmentally, than conventional petrol. As a result, while ethanol-petrol blends may have a part to play in the future of British motoring, we wouldn’t be hurrying to make the switchover just yet.

About The Author

Jon Le Roux is co-founder and company director of The Car Loan Warehouse. Being a mad engineering and motorsport enthusiast, I spend more hours than is healthy, watching, reading or talking about cars, boats, motorbikes…..basically anything with an engine.