FLEETS running BMWs could find cars grinding to a halt as engines fall foul of rogue filling stations selling petrol with a high sulphur content. Already about 1,000 BMWs have had engines replaced as a result of the fuel, which eats through the coating inside the engines.

In total about 50,000 models could be hit by the problem, which only affects the six-cylinder aluminium engine - known as the M52 engine - in the 328i, 528i and 728i, manufactured between January 1995 and March 1998. With the cost for replacing each engine about £1,000, BMW's repair bill could run into millions of pounds.

BMW GB says it is carrying out an investigation to try to find out which independent forecourts are selling the high-sulphur petrol, and says action will be taken if it is found stations are selling fuel at well over the normal sulphur level of 500 parts per million.

A spokesman said: 'If drivers stick to major known brands there shouldn't be a problem, and we are trying to find out where the high-sulphur petrol is coming from. So far the majority of cases seem to be confined to the north west. Anyone suspecting something is wrong with their vehicle can take it to the dealer for repairs under the warranty. All engines are covered for four years or 100,000 miles, if the problem hasn't happened in that time it's not going to.'