Hard-pressed motorists have enjoyed a respite from record-high fuel prices in recent days, according to AA figures.
Average UK petrol prices have fallen 4.08p in the past month and now stand at 138.40p a litre.
Diesel has fallen 3.58p since mid-April and now costs an average of 144.30p a litre.
The AA said monthly fuel costs for a family with two petrol cars had fallen by £8.66 and filling up the 80-litre diesel tank of a commercial vehicle now cost £2.86 less than a month ago.
It added that, on petrol sales alone, this had released £2.1 million a day from the pump into high street and other consumer spending.
But the AA added that the same two-car family would be £21.23 better off a month, and non-fuel consumer spending boosted by £5.1 million a day, if the 200-dollars-a-tonne or 10p-a-litre fall in the wholesale price of petrol across northern Europe was reflected at UK pumps.
The cheapest petrol is being sold in Yorkshire and Humberside (137.9p a litre on average), with the most expensive (139.5p) being in Northern Ireland.
Diesel is dearest in London and south east England, at 145.1p a litre, compared to the lowest average of 143.6p in northern England, north west England and Yorkshire and Humberside.
AA president Edmund King said: "A £2-a-tank saving for drivers eases some of the pressure on UK families and business, but there is so much further to go.
"It was noticeable that there has been a flurry of 2p-price-drop and fuel-voucher announcements since the tanker drivers voted not to strike last week."