About 600,000 owners of older vehicles need to check whether a new E10 unleaded petrol will damage their engine as the fuel is rolled out across the UK as part of an attempt to cut carbon emissions.

In the biggest change to forecourts since four star petrol was banned 20 years ago, the government has decreed that from September the standard, cheapest, unleaded petrol must be a 10% bioethanol mix.

The E5 unleaded fuel sold at forecourts until now contains 5% bioethanol.

Anyone filling up in recent weeks may have noticed that there are now two basic unleaded options – the new E10 fuel, and the familiar E5 – as fuel retailers gear up for the change.

While the government says that 95% petrol cars will be able to switch to the “greener” E10 unleaded without a problem, its impact statement on the switch suggested 600,000 cars and scooters and other early vehicles such as campervans – mostly those built in the early 2000s – will not run on the fuel.

If your car is one of them, you may have to start buying super-unleaded which retains the 5% bioethanol mix, but is typically at least 10p a litre more expensive. Those forced to switch will be paying around GBP5 extra each time they fill up – assuming an average family car with a 50-litre engine. Someone filling up once a week will face a GBP250-a-year fuel bill rise, at a time when prices are already at an eight-year high.

To help drivers find out if their car is affected, the government has launched a vehicle checker website. Plenty of cars built before 2011, at which point all cars sold were required to run on it, will be able to use the new E10 unleaded.

In some model ranges, owners of cars with one engine are being told it will be fine, while those of a similar model are advised not. For example, E10 petrol is cleared for use in all Toyota’s European petrol models made from January 1998, except two Avensis models with 2.0 and 2.4 litre engines.

Owners of a number of VW Golfs and other models built as recently as 2004 are also being advised to not to switch to E10 petrol.

The switch to greener petrol is part of the government’s move to net-zero CO2 emissions by 2050.

Bioethanol is produced from crops such as sugar beet, which is a renewable source.

Transport secretary Grant Shapps says the introduction of E10 fuel will cut carbon emissions by 750,000 tonnes per year – the equivalent of taking 350,000 cars off the road.

“Although more and more motorists are driving electric vehicles, there are steps we can take to reduce emissions from the millions of vehicles already on our roads – the small switch to E10 petrol will help drivers across the country reduce the environmental impact of every journey, as we build back greener,” he says.

The RAC says drivers who put the E10 fuel in an unsuitable car risk damaging its fuel system components. Classic car enthusiasts are likely to be particularly affected.

The RAC’s fuel spokesman, Simon Williams, says: “The switch to E10 petrol is clearly good news for the environment and will not affect the vast majority of the UK’s 33m drivers. However, many cars registered prior to 2002 shouldn’t use E10 as seals, plastics and metals may be damaged by its corrosive properties if used exclusively over longer periods. It’s vital that anyone with an older vehicle gets the message about the switch otherwise they could end up with a big repair bill.”

Meanwhile Edmund King, president at the AA, has warned fuel bills are set to rise for all motorists because the new fuel doesn’t go quite as far as the E5 unleaded that it replaces.

“Moving from E5 to E10 is estimated to reduce pump price petrol costs by 0.2 pence per litre. However, as the energy content of the fuel will also lower meaning motorists will have to buy more litres of fuel. Overall fuel costs for petrol cars are therefore estimated to increase by 1.6% as a result of moving to E10,” he says.

The move has one other, possibly unforeseen, consequence. People are also advised not to put the new E10 fuel, which will be clearly marked on the filling station nozzle, in petrol lawn mowers and other similar petrol-run garden machines, as they may not like it either. The owners of some boats will also have to switch to the more expensive super-unleaded, along with plenty of scooter and moped riders.

The government has committed to selling the E5 super-unleaded fuel for at least five more years. None of these changes affects diesel car users.