Petrol prices tumbled by a record amount last month but drivers are facing a postcode lottery when paying for fuel, according to the latest data.
The average price of a litre of unleaded fell 12p in August and now costs an average of 169.8p, according to RAC Fuel Watch.
That knocks almost £7 off the cost of a tank of unleaded and brings it back below £100 for the first time since early June.
However, the RAC believes that drivers are still be overcharged by as much as 8p per litre in some places as retailers fail to pass on the full savings in wholesale prices.
It has also warned of stark regional differences when it comes to fuel prices, with petrol up to 3.5p per litre more expensive in some areas and diesel as much as 4p per litre more expensive. It said that even among major retail chains, pricing was not consistent around the country.
Petrol prices soared to record highs at the start of July but have been consistently falling back since then, dropping from 191.53p per litre on 1 July to 182.11p on 1 August and 169.8p on 21 August. Diesel prices have also dropped from a high of 199.07p at the start of July to 183.71p at the end of August.
However, the RAC says that wholesale petrol prices continued to fall throughout August and retailers have failed to pass on these savings, resulting in averge petrol prices that are 8p too high.
Its spokesman Rod Dennis said: “Twelve pence a litre is a lot to come off prices in a single month so there’s no doubt things could be worse, but in reality drivers of petrol vehicles are still invariably getting a raw deal at the pumps. For whatever reason, major retailers are choosing not to pass on in full the reductions in the wholesale price of unleaded they’ve been benefiting from for some considerable time now – and this continues to mean drivers are often paying much more every time they fill up than they should.”
Mr Dennis said that some retailers were offering fuel at close to the “fairer” price of 161p per litre but others were exploiting regional differences. He said: “There’s a real postcode lottery out there with prices varying wildly depending on where a driver is in the country. Drivers must shop around for the best deal they can, and we applaud those independent retailers who are doing their best to charge a fairer price for fuel and support their local communities through this incredibly expensive time.
Cheapest and most expensive regions for fuel
The latest figures show where drivers are getting the best deal on petrol and diesel prices as well as which regions have seen the biggest changes since the start of August.
Drivers in the east of England enjoyed the sharpest drops, with petrol falling 12.96p per litre and diesel dropping 9.11p. However, the region still faced among the highest prices in the country. Petrol was 170.87p per litre and diesel was 184.4p compared with national averages of 169.8p and 183.71p respectively.
London saw the next-largest reduction in petrol prices - down 12.89p but - also remained among the most expensive places for petrol and diesel, while the East Midlands saw the second sharpest drop in diesel costs, falling 8.97p. The smallest cuts were in Northern Ireland where petrol fell 9.97p and diesel 5.91p but drivers there still enjoyed the lowest overall prices at 167.2p for petrol and 180.58 for diesel.
Mr Williams advised drivers searching for the cheapest fuel near them not assume that supermarkets were always the best value.
He said: “The best advice for filling up is no longer to assume the supermarkets are the cheapest, but to shop around as it’s highly likely you’ll find an independent retailer which is doing the right thing and fairly reflecting their lower wholesale costs by charging a lower price.”