E10 Petrol

Since 1st Sep 2021 E10 petrol has replaced E5 at regular unleaded pumps throughout the UK

What is E10?

E10 stands for 10% Ethanol (E5 is 5% ethanol). In other words, the fuel is 90% petrol and 10% bio-ethanol. Bio-ethanol is ethanol which has been produced from plant matter

Why do we have to have it?

Governments around the world see the addition of bio-ethanol to car fuel as a ‘green’ move because when ethanol burns it produces few harmful emissions, and the CO2 it produces is offset by the CO2 absorbed from the atmosphere when the plants, such as sugar beet, are growing. Optimists regard this as a carbon neutral process, though many arguments exist about the ethics of clearing forest and growing crops for fuel instead of food.

As a fuel what are ethanol’s problems?

Ethanol absorbs water from the atmosphere and effectively dilutes the fuel if left for a long time. The absorbed water can create corrosion on steel parts such as tanks and metal pipes

Ethanol is a solvent and can attack and soften rubber hoses, some types of fuel tank, seals in the fuel system, and alloy parts such as carburettors

Is it ok for classic cars?

In general, NO. Pre-2005 cars will probably have non-ethanol proof fuel hoses, and pre-2000 cars almost certainly. These will degrade with exposure to high concentrations of ethanol, eventually dissolving leading to clogging of fuel pumps, injectors, fuel pressure regulators, and weakening the hoses such that they may leak or burst. Later classic cars including facelift XJSs have the fuel pump(s) inside the fuel tank, connected to the outside world via internal rubber hoses. These are thus attacked by fuel from inside and outside and are the first to leak or dissolve.

Cars with fuel tank emissions control hardware will not suffer too much from water absorption since the fuel system is closed to the atmosphere, but over months or years some atmospheric water will get in. Earlier cars with essentially open fuel systems will absorb water quite quickly.

Cars with alloy carburettors will likely suffer internal corrosion and probably leakage from seals and gaskets.

What can I do?

• The easiest solution is to use only E5 petrol which is still to be had in the form of premium 98 octane fuels such as Shell V-Power and BP Ultimate. However, this is likely to be phased out over the next few years, and it is more expensive. At this time (September 2021), such premium fuels are not known to damage any classic car, and there are other benefits in that they contain additives to keep the system cleaner. Most classic cars can’t benefit from the increased power available from higher octane fuels, though those with re-mappable ignition systems can.
• One can replace all the fuel hoses with ethanol-proof type. This will remove the greatest problem: Hose damage. For the Jaguar XJS, Series 3 XJ and later cars the fuel system is closed so water aborption is not a great problem if the car is used such that it consumes several tanksful per year. For earlier cars such as the E Type, Mark 2 etc replacing the hoses will not be enough since they have alloy carburettors. Other than sticking with E5, we don’t know of an easy solution.

How can KWE help?

We can replace all your fuel hoses with ethanol-proof type. Costs vary from £500 to £2500 depending on engine size and whether there are in-tank pumps.

We advise owners who do not use their classic car often to keep the tank topped up to the brim with E5. This reduces the amount of water that can be absorbed, and minimises tank corrosion. Failing that, you will need to drain your tank(s) and fuel lines before storage.

The future

A big problem is that there is no body of research quantifying the damaging effects of E10 (and beyond) on specific older cars, so there is a big element of trial and error. KWE is of course monitoring the situation and using E10 in a range of our own cars to see what happens. We will keep our readers informed. We have had only one case of damaged fuel hoses, from an XJS which spent most of its life in France where high ethanol fuel was not marked on the pumps. The in-tank hoses dissolved, clogging the fuel pump, though this was far from obvious.

Hopefully, some additives will be developed where high ethanol fuels can be rendered safe for older cars, and E5 fuels will still be available indefinitely. Lobby your MP now!