The truth about E10

We enlist an expert to answer your ‘green petrol’ questions

TECHExpert confirms real impact for bikers

In September 2021 ‘E10’ will become the new standard unleaded petrol in UK filling stations and the changeover has sparked concerns. Are these worries valid? We’ve taken your questions to an industry expert.

What is E10 petrol and why is it being introduced?

At the moment, regular unleaded is ‘E5’, which means it has no more than 5% ethanol content. Ethanol is simple alcohol and as its name suggests, E10 has a higher content. “In the UK, E10 will be petrol containing at least 5.5% and up to 10% ethanol – with the remainder made up principally of hydrocarbons,” says Jamie Baker, from the UK Petroleum Industry Association. “As almost all ethanol blended into petrol in the UK is renewable in origin – the fuel manufacturing greenhouse gas emissions – known as ‘well-totank’ emissions – are significantly lower than fossil-derived petrol.”

Will it damage my bike?

Unlikely. Ethanol is a solvent, so can attack some gaskets or seals on older bikes that weren’t designed with it in mind, as well as the resins used in fibreglass. It’s also been known to cause some older plastic tanks to swell. But the vast majority of bikes, even older ones, are not affected. When it comes to actually burning E10, anything with O2 sensors in the exhausts will be unaffected as they can automatically recalibrate for the best combustion. On older bikes with carbs or early injection systems, E10 can cause a slightly lean running condition but this can be tuned out.

If I need to use more throttle to get the same performance from E10, does this outweigh the environmental benefit?

Ethanol is actually higheroctane than petrol but it is less energy-dense than pure petrol. The difference is small (33.18 megajoules per litre to 34.2 MJ/L), so a 5% increase in ethanol makes for a very small change in efficiency. Fuel efficiency could fall by 1% but Baker tells us: “Any increases

‘Ethanol can attack some gaskets or seals’

in consumption outweighed by the reduction in well-to-tank greenhouse emissions.”

Can I leave E10 in my tank while my bike is stored?

No petrol likes being stored long term, with BP saying that storage life is six months if the fuel is kept under 20°C or three months nearer 30°C. Ethanol differs from straight petrol because it’s hygroscopic, so it attracts water. For the ethanol to absorb enough water to cause ‘phase separation’, where the ethanol water mix separates and sinks to the bottom of the tank, it would need a very humid environment (not something we really suffer from) and months of sitting still. If you’re concerned you could fill your tank with E5 before storage.