New research has shown that fleet managers should insist their drivers do not fill up at motorway filling stations except in an emergency.

The findings show motorway fuel prices are currently 10p more per litre than supermarket forecourts located just off motorways, which means it is costing fleets an extra £5.50 to fill up a typical car every time their drivers chose the convenience of a motorway service station over an off-motorway supermarket.

The RAC found that, on average, supermarkets are charging £1.11 a litre for unleaded petrol compared to £1.21 at motorway service stations, and an average diesel price of £1.24 at supermarkets compared to £1.34 at motorway service stations.

RAC spokesperson, Louise Zucchi, said these extra costs are inexcusable.

“Most service stations have the infrastructure and buying power of supermarkets like Asda - which led the recent price cuts at the supermarket pumps and has now introduced a fuel pricing policy – but they don’t seem to be using that commercial strength to help motorists,” she said.

“We hope motorway service station operators will consider what more they could do to ease the pain at the pumps.”

Until that happens, the RAC is recommending that drivers exit the motorway when the need to fill and use a local supermarket filling station instead.

“By spending a couple of extra minutes to come off motorways, drivers really can be quids in by taking advantage of significant fuel savings,” said Ms Zucchi.

Spokesman for the Petrol Retailers Association, Ray Holloway, said the RAC findings were “a statement of the bleeding obvious”.

Motorway services have a higher cost base than local filling stations and, unlike supermarkets, do not reduce fuel prices to tempt buyers into their stores, he said.

“The advice has always been that motorists have a choice about where to fill up.”