Petrol prices could fall by another 3p over the next two to three weeks, the Basingstoke-based AA said today.
The average price of petrol now stands at 136.89p a litre following supermarket cuts, already 3.02p lower than a month ago.
The AA said average petrol prices could fall to about 134p a litre soon with wholesale fuel prices falling.
Average diesel prices have fallen 4.62p to a current 141.76p a litre, AA president Edmund King said: "The last 12 months have shown pump price volatility is more acute than ever, driven largely by speculation."
Supermarket giant Sainsbury's has announced it will reduce its forecourt prices by 3p a litre.
The cut will come into force tomorrow at all of the store's 266 petrol stations across the country, and also covers diesel. Last week the AA said that UK petrol prices had fallen 4p and diesel by more than 3.5p in the past month.
Asda, Tesco and Morrisons have all announced price cuts in recent weeks.