The introduction of E10 petrol in September 2021 marks the biggest change in what we fill up with at the pumps since leaded fuel was banned under EU ruling in the year 2000, around two decades after its disastrous effect on public health and atmospheric pollution was really established.

As its name suggests, E10 – which has taken the place of regular 95 RON at the forecourt – contains 10% ethanol, double that of the previous E5 fuel which contained, as its name suggests, 5%.

While the switch to E10 is undoubtedly a good one for the environment and thus all of us as a whole - the UK government is predicting it will lead to a reduction of over 750,000 tonnes of CO2 emissions per year - it is not such an ideal scenario for owners of classic cars who may be concerned about what effects this new high-tech fuel will have on their beloved and decidedly low-tech classic cars.

The issues stem from the fact that E10 fuel is hygroscopic - meaning it absorbs water – and that Ethanol’s molecules are smaller than the other components in petrol - meaning it is more easily absorbed by elastomer materials such as rubber and plastic, materials found throughout any fuel system. It doesn’t stop there either, it can also cause metals to corrode under certain conditions too and to top it all off, it even reduces fuel consumption by approx. 1%!

Finally, E10 fuel tends to cause engines to run leaner, something modern car’s ECUs and Lambda sensors can easily account for but not so when it comes to older engines which require the air/fuel ratio to be manually adjusted to suit.

With all this in mind, and coupled with the fact we don’t yet know the long term effects E10 fuel has on the combustion engine, there are steps the classic car owner can take to ensure their beloved car isn’t negatively affected by this change in what goes in its tank.

First of all, it’s important to bear in mind how often one drives their classic car. If the car is used sparingly and off the road for extended periods of time it is vital to not leave the tank full of E10 as it will absorb moisture leading to corrosion of components in the fuel system.

However, do not store a car with no fuel in the tank as this too can lead to corrosion and the shrinking and cracking of elastomers and gaskets. If a car is to be stored use an E10-free fuel – available at most major filling stations as E5 Super Unleaded.

As ethanol is a solvent it can quickly remove historic deposits in the fuel system and as such it is vital to check filters and lines regularly to ensure no restrictions or blockages have occurred from the degradation of rubber or plastic components.

With that in mind, it is also important to keep on top of the condition of all parts of the fuel system; everything from plastic carburetor floats and gaskets to even the tank itself. 

Fuel additives can help mitigate the negative effects of E10, but they are not a guaranteed solution and should only be seen as a preventative, temporary measure.

Whether your classic is in regular use or only brought out on the sunniest of special occasions, the Hexagon Classic workshop is perfectly positioned to keep it in optimum health by inspecting all areas of its fuel system, cleaning and replacing parts as necessary to ensure long term reliability and avoid costly repairs in the future.

E10 fuel may not be going anywhere but as always, our specialist technicians are here to ensure your car stays healthy, happy and ready for that perfect road trip at a moments notice.