Motorists travelling to visit loved ones this Christmas face a postcode lottery at supermarket petrol pumps with the cost of filling up a family car varying by up to £8 across the country.

A Sainsbury’s garage in Frome, Somerset, has been identified as the most expensive supermarket fuel outlet in the country – charging 141.2p per litre of standard petrol.

In contrast, a motorist who fills up at another Sainsbury’s fuel station 170 miles away in Braintree, Essex, is only being charged 126.9p per litre, according to the latest data released by the retailers – which is more than 14p per litre cheaper. For someone filling up the petrol tank of the average family car, that would be a difference of nearly £8 for the same Sainsbury’s fuel.

Analysis of the data published by the big four supermarkets reveals a wide range of prices charged for fuel within the UK. Asda petrol also varies in price by 14p per litre depending on which part of the country you choose to fill up in. Morrisons is charging customers in Hartlepool nearly 9p per litre less than drivers who fill up at Morrisons garages in Denbigh and Rhyl, North Wales.

And Tesco customers at two garages in Northern Ireland will pay nearly 12p per litre less than their counterparts in eleven other supermarket petrol stations around Scotland and England.

Our exclusive interactive map shows which supermarket is charging the least for petrol in each part of the country, according to the latest data.

The average price of supermarket fuel is now around 133.5p per litre for standard petrol but Tesco is charging a penny more than its rivals, coming it at 134.5p a litre. Asda has the slight edge over its rivals by offering the cheapest supermarket petrol in 96 out of 338 local authority areas including large areas of Scotland, Northern Ireland and the South West of England.

However, in 87 other areas it’s Morrison’s which has the cheapest fuel on average and Sainsbury’s has the best value on offer in 79 districts. The Competitions and Markets Authority has called on supermarkets and other petrol retailers to lower the margins charged to motorists, with claims that drivers are being ‘ripped off’. Earlier this year the CMA reported that drivers had paid a total of £1.6 billion more for petrol than they should have done, due to the high margins.

Petrol prices have fallen from a 2024 highpoint of 150p per litre in May and motorists were spared a feared hike in fuel duty in the Labour government’s first budget. The government will also be requiring all retailers to report latest prices within 30 minutes of a price change.

RAC head of policy Simon Williams said: “While conditions are clearly better for drivers this Christmas than previous ones, we’re still conscious that prices at the pumps could be slightly cheaper if retailer margins were lower.

“We hope the Government’s commitment at the Budget to introducing a mandatory fuel price finding scheme next year will spark competition and lead to a fairer fuel retailing landscape that delivers better value for drivers wherever they fill up.”