The UK average price of diesel dropped 1.27p to 130.01p, while unleaded came down by 1.32p to 120.92p in January.

This means it now costs an average of £65.78 to fill up a 55-litre family car with petrol – £6 less than it did at the end of October. A tank of diesel, however, has only come down £3.78 to £71.50 over the same period.

The data from RAC Fuel Watch also shows that prices at the country’s four biggest supermarkets were lower still, by an average of 3p a litre at 116.66p for petrol and 125.43p for diesel.

However, at motorway service areas, a litre of unleaded set drivers back 138.87p and 147.55p for a litre of diesel.

RAC Fuel Watch figures show the wholesale price of petrol stayed flat in January while diesel increased by 2p a litre, but when compared to retail prices they were low still low enough to demand pump price reductions during the month. Sadly for drivers though, retailers decided not to pass these on, says the RAC.

If retailers were to pass on existing savings in their wholesale costs the price of petrol ought to reduce by 3p a litre in the next two weeks, and diesel by 2p a litre, it claimed.

“The story behind the simple forecourt average figures is quite disturbing,” said RAC fuel spokesperson Simon Williams.

“Looking at the wholesale data over the last two months reveals that we should have been paying far less for our petrol and diesel than we have been.

“Unfortunately, three of supermarket fuel retailers appear to have changed their pricing policies for the long term by increasing the margin they take on a litre of petrol to about 2p. This has meant the average price of unleaded has not reduced by as much as it should have because smaller retailers nearby haven’t had to lower their prices as much in order to compete.”

Williams continued: “We understand retailers are free to charge what they like for their fuel and that it’s then up to consumers whether they’re prepared to pay their prices or not.

“Unfortunately, consumers don’t have an easy way of knowing whether they are being charged a fair price so they have to trust they aren’t being ripped off. That’s why we always encourage drivers to check the current average price of petrol and diesel, and see if they can beat that price when paying for fuel locally.

“Combine this with the fact some bigger retailers vary their prices from location to location, fuel is an essential purchase for most people and that shopping around is not that easy, and you have the perfect recipe for drivers being charged over the odds for what is essentially a commodity.”

Regional fuel price variation

Regional average unleaded pump prices

The North West saw the greatest reduction in the price of unleaded in the UK with 1.36p coming off a litre taking it to 118.95p. The North East, however, had the cheapest petrol at the start and close of January (118.98p and 117.95p). The South East was once again the most expensive. 

Unleaded	02/01/2019	31/01/2019	Change
UK average	120.72	119.60	-1.12
North West	120.31	118.95	-1.36
East	121.65	120.37	-1.28
Wales	119.96	118.76	-1.20
South East	121.76	120.62	-1.14
Scotland	120.03	118.91	-1.12
South West	121.23	120.16	-1.07
West Midlands	120.47	119.41	-1.06
North East	118.98	117.95	-1.03
Yorkshire And The Humber	119.82	118.90	-0.92
East Midlands	120.54	119.65	-0.89
London	120.80	119.94	-0.86
Northern Ireland	119.38	118.56	-0.82

Regional average diesel pump prices

The East of England enjoyed a 1.59p drop in the price of diesel, surpassing the UK average fall of 1.27p. Northern Ireland has the cheapest diesel at 127p a litre while the South East has the dearest at 129.57p.

Diesel	02/01/2019	31/01/2019	Change
UK average	130.01	128.74	-1.27
East	130.73	129.14	-1.59
North West	129.85	128.38	-1.47
South East	130.95	129.57	-1.38
East Midlands	129.98	128.70	-1.28
London	130.36	129.14	-1.22
Wales	129.49	128.27	-1.22
Northern Ireland	128.20	127.00	-1.20
North East	128.97	127.80	-1.17
South West	130.25	129.11	-1.14
Yorkshire And The Humber	129.33	128.25	-1.08
West Midlands	129.52	128.51	-1.01
Scotland	129.58	128.93	-0.65