Motorists could save up to £468 annually by shopping around for fuel at supermarkets like Tesco, Sainsbury's, Morrisons and Asda, according to the Competition and Markets Authority (CMA).
The CMA's latest assessment found that elevated wholesale costs were the main driver behind recent petrol and diesel price increases through to the end of April.
Sarah Cardell, chief executive of the CMA, said: "We know prices at the pump are putting real pressure on drivers' pockets."
The watchdog calculated that motorists could save as much as £9 per tank by using price comparison platforms and navigation apps to find better deals.
Matthew Briggs, CEO of Right Fuel Card, confirmed that supermarkets offer more affordable fuel than branded alternatives due to intense competition. He warned drivers to avoid motorway fill-ups due to their "excessively high prices".
The CMA remains concerned about weak competition in the fuel sector and expects retailers to rapidly pass on any wholesale price reductions to drivers.
