The cost of filling up a car with petrol is £2 less than a month ago, according to new figures.
A six-year low in the price of oil helped bring the average cost of petrol down by 4p a litre to £1.12 in the last week of August, RAC Fuel Watch said.
Diesel also continued to drop throughout the month with a further 5p shaved off a litre, taking the average price down to £1.10, keeping it below petrol.
In the run-up to August oil was at a consistent 60 US-dollars a barrel, but dipped to a low point of 41.87 US dollars on August 24.
RAC fuel spokesman Simon Williams said: "We thought July had been a good month for motorists but August proved to be better still due to world oil prices reaching their lowest since February 2009.
"Diesel drivers have benefited the most this summer due to a new supply of diesel from Saudi Arabia bringing the wholesale price down.
"They are now paying £5.60 less to fill up than they were at the beginning of July whereas the savings for petrol motorists have only just kicked in with the drop in the price of oil feeding through into lower wholesale and retail prices."
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