Motorists have been flocking to rival petrol stations after two supermarket chains confirmed they had been hit by the faulty fuel fiasco.

Chains across Oxford reported a surge of up to 45 per cent in sales as Tesco was forced to drain and refill its tanks at its five Oxfordshire forecourts over the weekend.

On Friday, it confirmed it had found traces of silicon in samples of petrol and made the move as a precautionary measure.

Silicon is believed to have caused thousands of motorists' cars to break down because the contaminant damages engine oxygen sensors. About 30 drivers have contacted the county's trading standards department.

Business was booming at the Esso Service Station in Oxpens Road, one of the firms unaffected by the contaminated fuel.

On Saturday, staff reported so many customers had come to fill up they had almost sold out, with sales up more than 40 per cent.

Service station manager Sarah Griffin said: "People are asking how our fuel is and we have had no problems. They won't go to the supermarkets just in case."

The London Road Shell garage in Headington, Oxford, also had a large increase in customers.

Supervisor James Garrett added: "I think the problems at Tesco have had a knock-on effect for everyone."

Murco in Between Towns Road, Cowley, had also seen a rise in new customers over recent days.

About 5,000 motorists across the country may have bought the contaminated fuel and been charged up to £200 to fix engine sensors.

Morrisons and Tesco have been named as the two outlets where the fuel has been sold after traces of silicon was found in storage tanks at their main supplier in Essex.

Harvest Energy said "unusually high levels of silicon" were found in four storage tanks at the Vopak site.

Compensation for drivers who paid to fix their cars after filling up with the rogue petrol could run into millions of pounds.

To secure compensation, claimants first have to go to the station where they bought the petrol with the receipts, but there needs to be a declaration of responsibility from the supermarkets before claims can be made.