E10 Fuel Explained​

Jaguar E Type Roadster Eagle

The recent introduction of E10 fuels as standard fare on forecourts across the UK has thrown up a challenge for drivers of many classic vehicles, including those lucky enough to find themselves behind the wheel of a pre-war and post war cars.

Here we offer you our views on the issue, and suggest a way forward that should keep you, and your car, happily bowling along.

  • Although many cars run on E5 without significant problems, doubling the amount of ethanol in the fuel can cause a variety of issues in older cars. The main concern around the new industry-standard E10 fuel is that it can eat through old flexible fuel lines, seals and gaskets due to its smaller molecular structure. This can lead to swelling, shrinking and cracking of seals and flexible pipes with potentially hugely serious consequences.
  • E10 fuels are more corrosive to some metal components, ethanol has increased acidity, conductivity and chloride content compared to conventional petrol. It is therefore important to make sure that any metal in contact with E10 is regularly checked, solder in things like fuel tanks and carburettor floats is particularly vulnerable.
  • Air / fuel enleanment is also an issue. Ethanol contains around 35% oxygen by mass and when it burns it makes the mixture leaner and therefore hotter. In extreme cases this could lead to melting of some parts inside the engine, valves and pistons. Re-tuning the carburettors will easily solve this issue but should be carried out using a lambda sensor to ensure that it is correctly set.
  • While this all sounds frightening, particularly as the roll-out of E10 continues nationwide, there appears to be a simple solution for drivers of most classic motor cars. Simply put, the advice is to switch away immediately from E10 unleaded fuel and opt instead for Super Unleaded. Our understanding is that Super Unleaded will remain a ‘Protection Grade’ fuel, with the intention of it being retained for use in vehicles incompatible with E10 unleaded.
  • We are, of course, happy to chat to you about this issue if you have any remaining concerns, but this simple and relatively inexpensive workaround – using Super Unleaded at all times in your car – should keep you on the road and unaffected by the problem. If you are unable to be sure of using protection grade fuels then we are happy to set your car up to run on the new E10 fuel.