Millions of motorists face being forced to buy expensive super-unleaded petrol under radical new plans to introduce greener fuel across the UK.
The Department for Transport (DfT) wants to adopt a European directive that will increase the amount of ethanol in premium unleaded fuel from 5% to 10%.
However, nearly a third of the cars on the road today might not be able to use it without modifications.
As a result, only super-unleaded – which costs 5p a litre more – will remain at 5% ethanol and will be safe to use in cars built before 2000.
Germany has rejected the fuel because of fears about the damage it does to vehicles.
The UK is poised to follow France, however, and embrace the new fuel composition – and it could be introduced to Britain’s forecourts from January.
Ethanol is seen largely as an environmentally friendly alternative to petrol. It is made from crops such as sugar cane in Brazil and soybean in the US and is significantly less polluting because it does not produce sulphur dioxide or lead emissions.
However, the corrosive effect of ethanol means increasing the level above 5% can damage engines.
The DfT consultation says older, carbureted cars built before 1993 cannot use the 10% blend – and only cars built after 2000 have been designed to use it.
The government claims all cars can be adapted to cope with the fuel.
More than 40% of cars in France were unable to use E10, as it is known, when it was introduced in April 2009.
The French government said the fuel was suitable only for cars built after 2000 and that all other motorists should steer clear.
According to the Society of Motor Manufacturers and Traders (SMMT), 30% of cars in the UK are at least 10 years old.
Vanessa Guyll, technical specialist with the AA, said ethanol had proven to be “incredibly corrosive” for older vehicles.
The motoring group said the move to a higher concentration would force many people to pay extra to fill up.
Ms Guyll said: “We are short of space on forecourts, so the new E10 blend will take the place of unleaded, although 5% ethanol will still be available in super-unleaded.
“However, it is 5p a litre more expensive on average.”
She added: “We have heard of no problems with the E10 blend in modern cars and it is widely used in America.
“But it is a bit too aggressive for standard rubber pipes found in older cars because it is corrosive and it may cause other problems.”
A spokesman for the RAC said motorists with older cars should contact the manufacturer before using the fuel.
He said: “All modern-day cars should not have an issue running on the 10% mix. There are potential problems for older cars and motorists should take advice from manufacturers if they are unsure.”
Westminster SNP transport spokesman and Western Isles MP Angus MacNeil was alarmed at the prospect of further price rises.
“At a time when fuel prices are already causing real pain, the prospect of an extra 5p a litre rise is frightening,” he said.
“While supporting the development of greener fuels, the Treasury must not add to the burden already faced by motorists. Forcing up forecourt prices is absolutely the wrong thing to do while the economy is in such a fragile state.
“The need for a rural fuel derogation is now urgent, and we must certainly have action before the VAT rise in January, which will hit rural Scotland especially hard.”
The price of fuel has risen dramatically this year and a further rise is expected in January when VAT goes up.
Prime Minister David Cameron said recently that the UK Government was seriously considering a pilot scheme to reduce fuel duty in a remote area in the Highlands and islands.
The fuel derogation scheme is understood to be backed by Chief Treasury Secretary Danny Alexander, the Liberal Democrat MP for Inverness, Nairn, Badenoch and Strathspey.
The government consultation on the ethanol proposals will end on September 30. The plans are expected to be laid before parliament before the end of the year.
If the move is approved, the DfT proposes to change the rules to permit the 10% ethanol blend from January, although it is not expected to be available across the UK until 2015.