Retailers and suppliers said they were carrying out tests on fuel but had so far found no evidence of any abnormalities. Contamination with ethanol is thought to be the likely cause.
Trading standards said they were looking into complaints from up to 100 motorists in southeast England where the problem is centred, particularly at Tesco’s and Morrisons superstores.
‘Officers are investigating these complaints and samples of fuel from some of the affected cars are currently being tested for contamination, as are the contents of the pumps from which the petrol was drawn," said Ian Hillier of the Trading Standards Institute.
‘The problem appears to be restricted to unleaded petrol and motorists experiencing problems with their cars should take them to a garage.'
Drivers who think they have been affected are advised to keep their receipts as proof of purchase of the fuel in order to make a claim. Trading standards also recommend getting a garage to take a sample of the fuel. Fuel contamination is not covered by a manufacturer's warranty.
The UK Petroleum Industry Association (UKPIA), which represents the nine main refining companies in Britain, said the problem did not seem to be widespread but was limited to London, east and southeast England.
'UKPIA is aware of reports of exhaust sensor failure in a significant number of petrol-engined cars,' it said.
This had caused ‘rough running of the engine or shut-down of the engine management system.
‘We have no reports of quality issues with petrol supplied from UK refineries,' UKPIA said, adding that the source of the problem might be a batch of fuel supplied to 'some large independent retail sites’. Tesco said it was investigating reports that drivers had experienced problems after filling up at its forecourts. ‘We are aware that customers of other supermarkets have also reported difficulties,’ a spokesman said.
Greenergy, which supplies 'greener' fuels, said its ‘extensive’ tests on the batch of fuel supplied to Tesco and Morrisons showed that it met industry standards, but it was continuing its investigation.
A spokeswoman said the fuel contained up to 5% bio-ethanol, which was within permitted limits
Christopher Macgowan, Society of Motoring Manufacturers’ chief executive, said the contamination was ‘hugely serious’ and on a scale he could not recall in all his time in the industry.
The petrol is believed to have been affecting oxygen sensors, which are part of the engine management system. They help a car run smoothly if it is operating normally or help it shut down if there is a problem.
Mr Macgowan said there had been a run on the components in recent days, leaving some drivers with their cars off the road for two to three days because a replacement was not available.