The average price of petrol and diesel fell by 6.5p in September – the ninth biggest monthly drop seen since 2000, new data from RAC Fuel Watch* shows.
A litre of unleaded averaged 134.79p, down from 141.26p at the start of the month while diesel fell from 146p to 139.5p. This means drivers are now saving £3.60 every time they fill up an average 55-litre family car. A full fill-up with petrol is now £74 and a tank of diesel is just under £77.
The drop at the pumps has been sparked by the continued reduction in the cost of a barrel of oil from $78 at the beginning of September to $72 at the end; the price was nearer $90 in early July. This, combined with a slightly stronger pound, means wholesale fuel, which is traded in dollars, is cheaper for retailers to buy.
Since the start of May petrol has tumbled 15.5p from 150.3p a litre, which equates to an £8.50 saving on a complete fill-up, while diesel has come down by a whopping 18.5p from 158p, saving drivers £10 on a full tank. 
Looking at the current delivered wholesale price of petrol, which stands at 99p a litre, and diesel, which is 103p, the RAC hopes pump prices will continue to fall over the next two weeks, possibly by as much as 4p a litre, as retailers pass on the savings they are benefitting from to drivers.
Drivers who buy their fuel at one of the big four supermarkets are currently saving 3p a litre compared to the UK average as petrol is 131.86p (UK average – 134.79p) and diesel is 136.47p (UK average – 139.5p).
RAC head of policy Simon Williams said: “Drivers will be very pleased to see prices at the pump not only continuing to fall but dropping by 6.5p in just a month as this translates to saving £3.60 on a full tank.
“Since the start of May prices have come down dramatically, with 15.5p being shaved off unleaded and 18.5p off diesel.
“The reductions have primarily been driven by a drop in the price of oil from above $90 in early April to below $70 briefly in mid-September, supported by a slightly stronger pound which makes wholesale fuel cheaper as it’s traded in dollars.
“With analysts predicting oil may continue to fall on the back of a weakened global economy and Saudi Arabia upping its output to regain lost market share, the immediate future on the UK’s forecourts looks considerably brighter for drivers.”
Motorists looking to save money on their fill-ups should take advantage of the fuel finder feature in the free myRAC app. The app can be downloaded for free from the App Store or Google Play.
Up to nine searches a day can be made over a two, five or 10-mile radius, with each giving the five cheapest prices.
The online RAC Fuel Watch resource has more information about the average price of petrol and diesel at the big four supermarkets and at motorway services. It also features graphs showing average prices since 2000 as well as a daily financial breakdown of the cost of a litre of petrol and diesel.
