Motorists unaffected by the contaminated fuel crisis should consider replacing the petrol in their tanks anyway.
Ray Holloway, director of the Petrol Retailers' Association, said drivers should consider getting fresh fuel even if their vehicle is not suffering any problems.
"Motorists who have not been affected could save themselves a bill by changing the petrol in their tanks. That would be my recommendation."
His comments came as investigations by trading standards officers continue into claims that some service stations and supermarkets sold suspect fuel.
Reports of malfunctioning vehicles are concentrated in south-east England, but complaints have also been made across the country.
The spotlight is on fuel sensors that have failed in some vehicles, probably because of faulty petrol. As a result, engine management systems cut power to prevent further damage, allowing drivers to only "limp home".
Manufacturers are working flat out to provide replacement parts after garages ran out of stock as they struggle to cope with demand.
Owners of a wide range of vehicles have reported their engines juddering, misfiring and suffering a loss of power. They face bills of more than £1,000 to replace the damaged parts, and some have contacted solicitors to seek compensation.
Independent oil company Greenergy said it was testing fuel supplied to Tesco and Morrisons to see if it was faulty. A spokesman said "extensive" tests on the batch of fuel supplied to the supermarkets showed that it met industry standards.
Both supermarkets said they had tested their stocks of unleaded fuel and not found any contamination or abnormalities.
