Ethanol in Fuel

I have been asked several times about the amount of ethanol being added to petrol to satisfy the ‘green lobby’ and EU regulations. As with all these things the answer is it’s not straightforward. Petrol companies are permitted to add up to 5% ethanol without declaring it. I believe most major suppliers are currently pretty close to this figure. It is worth noting that there is some pressure for the EU (and that would include us) to go up to 10% without companies having to declare it.

It is claimed that even at 10% the amount is unlikely to cause damage to a ‘standard car’. From reading articles I would suggest that classics are not ‘standard cars’ in this respect – more later.

It is possible for far larger amounts of ethanol to be added provided this is declared by the retailer at the point of sale. Some garages are currently selling E85 petrol and as the name suggests this has 85% ethanol and this should only be used in cars where the manufacturer states in can be used.

Several overseas markets have sales of 100% ethanol but their cars are specifically modified and adapted for this use. Such countries include Brazil and South Africa.

So what can happen if fuel containing ethanol is used in older classic cars? There are many reports of different problems but the most likely ones fall into three groups:

Loosening of pre existing contaminants in petrol tanks and fuel systems. Here the ethanol almost acts as a stripper loosening deposits including rust from any surface it comes into prolonged contact with. This material can then block filters and carburetor jets.

Chemical reactions with existing rubbers, resins, plastics and sealants etc. The effects on resins glass fibre fuel tanks can be of great concern but ‘O’ rings can turn to a sort of mush and plastic fuel lines can either leak or turn brittle depending on chemical composition. Fuel tanks with rubber liners are at risk and this is one for the racing fraternity to be concerned about. Having said that there are some classics with tank liners which may also be at risk.

The final issue is, I believe, of importance not only to classic car owners but to all users of this stuff. Ethanol is hydroscopic (like some brake fluids). That means it attracts and retains water. This can come from any source including water vapour in the air. The greater the moisture content in the ethanol the less likely it is to burn. If saturated it simply will not burn. That means if a car is not used for long periods the amount of moisture in the fuel may increase to a point where the engine simple will not start. In this case the fuel system will need draining and fresh fuel added to rectify the problem. Not an issue if the vehicle is used regularly but may become one where a car is laid up for several months over winter say.

Short answer is that it is highly likely the fuel he purchased contained some ethanol probably less than 5% but still enough to potentially cause issues.

Chris Lee
Vice President & Competition Secretary
Lancashire Automobile Club (Est 1902