A price war is breaking out between petrol retailers as oil supplies return to normal after the chaos caused by Hurricane Katrina.
Esso confirmed it was lowering its UK petrol and diesel prices on Friday by up to 4p a litre, following similar moves by supermarkets Asda and Tesco.
Meanwhile, BP and Royal Dutch Shell also said they planned to cut prices.
But the cuts did not stop a number of campaigners from staging a "go slow" protest on the M4 motorway on Friday.
A convoy of 60 fuel price protesters' vehicles completed a crawl along the motorway in south Wales to protest at the recent price rises.
Fuel prices have been hitting record highs due to the knock-on effect of Hurricane Katrina in the US.
After the storm
The storm hit oil rigs and refineries in the Gulf coast of America, causing worldwide supply shortages in both crude oil and petrol that resulted in a corresponding rise in prices.
But with supplies now returning to normal, prices are stabilising.
On Friday, a barrel of US light crude oil was down $1.25 to $63.50, while London's Brent had slipped $1.38 to $62.28.
The UK Petrol Retailers Association and AA motoring organisation had both recently predicted that petrol prices would fall.
Asda and Tesco were the first to take the plunge, cutting forecourt prices by up to 4p a litre.
A litre of unleaded from Asda fell to 89.9p, down from this year's high of 93.9p, while diesel fell to a maximum price of 92.9p.
Esso said on Friday it was also cutting prices by 4p a litre, while BP said it would also make cuts this weekend, but did not specify how much they would be. Shell, too, said it was reviewing its prices.
UK petrol prices are among the highest in Europe, with 67% of the total cost going on tax.
"Drivers are still dismayed by what they are paying at the pump," said petrol analyst Ruth Bridger.
But with the cost of crude oil back below $64 a barrel, petrol prices should continue to fall barring any man-made or natural disasters affecting oil supplies.