A combination of supermarket price wars and a sharp fall in the global price of oil saw the average price of unleaded drop from over 136p per litre to 133.82p.
Diesel declined from almost 140p per litre to 137.90p, the information company Experian Catalist revealed.
J Sainsbury has turned up the heat in its battle against other petrol providers by offering a 10p per litre discount to its customers.
Rivals Asda and Tesco had slashed three pence per litre off the cost of petrol, after the International Energy Agency (IEA) said it would release 60m barrels of emergency reserves throughout most of this month.
The announcement saw the price of Brent crude plummet by close to $7 (£4.36) per barrel in the day’s trading – prompting some retailers to cut their own prices at the pumps.
Energy secretary Chris Huhne has called for supermarkets to also offer gas and electricity provision to homes.
“We welcome the reduction in petrol prices,” a spokesperson for the Road Users’ Association said, “but the key issue is that most of the cost of fuel is tax.” Tax accounts for over 60 per cent of the price of unleaded, it said.