Using E10 Fuel With Your MT

From September 2021 ‘E10’ will become the new standard unleaded petrol in UK filling stations, and the changeover has sparked concerns that it could cause poor running or even damage on some bikes. In this post we go over some of the frequently asked questions regarding the fuel, and how it will affect your MT.

What is E10 and why is it being introduced?

Previously, normal unleaded standard stuff was ‘E5’, which means it has no more than 5% ethanol content. Ethanol is simply alcohol, and normally comes from renewable sources so its ‘green’ compared to petrol from oil wells. As its name suggests, E10 has a higher ethanol content of up to 10%.

Will E10 damage my MT?

The fears about ethanol stem from a couple of its properties. One is that pure ethanol, being alcohol, is hygroscopic – it attracts water, even pulling it out of the air around it, unlike petrol, which separates from water.

In the right circumstances, the concern is that ethanol absorbs enough water to cause ‘phase separation’, where the ethanol/water mixture separates from the petrol and sinks to the bottom of the tank. In reality though, this isn’t a huge concern, as even in very humid environments phase separation doesn’t usually happen before the petrol itself has gone stale.

Another concern over the long term is that ethanol can become acidic, speeding up corrosion of some materials, but again this is only going to happen if the fuel is left in the tank for long periods of time. Ethanol is also a solvent, so can attack some gaskets or seals on older bikes that weren’t designed with it in mind.

Regarding fuel tanks, we have noticed that the original steel fuel tanks on MTs have been fairly quickly “finished off” during the last few years, with rust clearly accelerating around the fuel tap area of the tank. This is most likely caused by the aforementioned hygroscopic properties of E5 fuel. Unfortunately, this will surely only get worse with the new E10.

Force Motorcycles plastic fuel tanks are fully compatible with ethanol-based fuel, so there is no problem with these tanks.

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

The truth is that petrol itself doesn’t really like being stored for the long term. BP says that its storage life is one year in a sealed container, dropping to six months once that seal is broken at 20°C, or three months if stored above 30°C.

Even after just a few weeks, evaporation means that the fuel in your tank becomes denser (as the lighter components of petrol are the first to evaporate), which means the air/fuel ration in your engine will be richer when you start it.

As mentioned above, phase separation can also occur (where the ethanol absorbs water and separates) over long-term storage, but again this will only be one of your problems if fuel is left in a tank for that long.

For some years now we have noticed carburettor problems occurring in MTs which have been stored with fuel in the fuel system, particularly the carburettor.
If your bike is to be laid up for any length of time, it is advisable to run it out of fuel, and even drain the carburettor. Any fuel in the tank should be drained off and the tank allowed to aerate and dry.

There are probably more inherent carb problems with the CV carb as fitted to the MT350 as standard, compared with the conventional carb on the MT500.
The small jets and small emulsifier tube in the HD carb, seem to suffer from periods of standing, even after a few months. Ultimately carb strip will be the only way of recovering the carb, once the deterioration from old fuel has occurred.

What can I do to continue using my MT?

In regular use, it would appear that using the new E10 fuel will not really make a lot of real world difference. These are bikes with finicky carburation at the best of times, after all!

Up-to-date reports seem to suggest that the premium fuels at the pump (expensive stuff such as SHELL Advance etc) will contain little or no ethanol – for now at least. So using these fuels should have a benefit for those of us running older bikes with carburettors.

To summarise, the main difference you can make to protect your fuel system, is to use the expensive premium fuel, and keep it fresh, making sure the tank is low or empty for storage, and that the carb is drained if anticipated lay-up is more than a few weeks.

Hopefully this article has proved useful to you, and helped put your mind at rest if you did have any doubts over using E10 fuel.

Thanks for reading, and happy riding!