Fleet managers are being warned that if their drivers use a biofuel that has recently gone on sale in Morrisons fuel stations they could invalidate warranties.

Industry service maintenance and repair expert Motorconsult has issued the warning about the new 30% biofuel, called B30, that is being rolled out across the network.

Alan Croft, of Motorconsult, said: “While you may think that fuelling your vehicle with this apparently greener fuel may appear to be good for the environment, it can be anything but for your warranty.

"A majority of manufacturers have said to us that using this fuel is not sanctioned for their vehicles and would cause the warranty to be invalidated.

"While it may be very tempting to use this seemingly greener fuel, especially as it’s priced at around the same as conventional diesel, we must say to all of our customers, please check with us or the manufacturer before allowing any of your drivers to use it.”

A statement from Morrisons said that there are warning notices on the orange-handled B30 pumps on their forecourts that advise customers to check with the vehicle manufacturer that the engine is compatible with the fuel before filling up.

The pumps are situated next to the black conventional diesel pump.

Motorconsult said that while the engine may run on B30, should a subsequent failure occur and the manufacturer is one that has not specifically approved the use of the fuel, then the warranty almost certainly would be invalidated.

It adds that potential bill to the customer for a replacement engine, could run to several thousand pounds.

Manufacturers that have said that B30 is not approved include Alfa Romeo, Audi, BMW, Chrysler, Fiat, Ford, Honda, Hyundai, Jaguar, Mazda, Mercedes-Benz, Nissan, Renault, Seat, Skoda, Toyota, Volvo and Volkswagen.

Vauxhall has approved it for some Vivaro and Movano LCVs but with conditions including replacement of the fuel filter at 24,000 miles and signing a ‘conditions of use’ document as well as providing VIN numbers of the vehicles intending to use the fuel.

Peugeot will sanction use of the fuel but says that a special dispensation is required to ensure that fuel quality standards are respected.

Citroën too, will sanction the fuel but also applies special restrictions.