Diesel drivers are being hit by an extra 20p a litre for fuel compared to petrol drivers despite there being “little difference” between the two fuels on the wholesale market, according to the RAC.

The RAC says retailers are subsiding petrol prices by charging more for diesel

Its data shows drivers are currently having to pay 168p a litre, compared to just 148p for unleaded. But the wholesale price of diesel last week was just 6p more than petrol (121.06p compared to 115.48p).

It means the cost of filling an average 55-litre diesel family car stands at £92.40.

By taking more than double the margin on every litre of diesel they sell – just under 20p – compared to the 8.5p on unleaded, the RAC says retailers are subsiding petrol prices by charging more for diesel.

Fuel spokesman Simon Williams said: “While our data shows petrol is generally being sold at a fair price at forecourts at the moment, drivers of the country’s 12 million diesel cars – as well as almost every white van driver – have every right to feel hard done by as they’re paying a huge premium for the fuel which in no way reflects its lower wholesale cost.

“For nearly a month, the gap between wholesale petrol and diesel prices has been less than 10p a litre and in recent days it has reduced to just 3.5p, yet average diesel prices at the pumps remain stubbornly high having fallen by only 2p since the start of February.”

It’s urging retailers to play fair and urgently cut the price of diesel to fairer levels, following the lead of Costco. The membership-only retailer cut 4p off diesel at its sites across the UK this week, meaning it is now charging an average of 154.7p – 13p less than the UK average and 11.5p less than the average at the UK’s big four supermarkets.

“The fact that Costco has been able to cut the average price of a litre of diesel by a massive 4p this week shows what’s possible, but we badly need other fuel retailers to treat drivers of diesel vehicles fairly,” added Williams.

“Even though the price of diesel is not being cut as quickly as it should be, the gap between the average prices of petrol and diesel has dropped to under 20p (19.99p) for the first time since 10 October 2022. If retailers now do the right thing this should reduce significantly, saving drivers who rely on diesel a lot of money every time they fill up.”

The RAC has been calling on the retailers, in particular the big four supermarkets, to cut their prices substantially for months after warning that there should have been much bigger drops following large reductions in wholesale costs during Q3.

Grant Shapps also waded into the debate in December 2022 as Business Secretary, writing a letter to fuel retailers that said he was concerned to see that the initial findings of the review into the fuel retailing sector by the Competition & Markets Authority (CMA).

Published on 6 December, the probe by the UK’s competition watchdog found that drivers had been hit by so-called ‘rocket and feather’ pricing on road fuel last year – particularly for diesel – and that it had been the most volatile 12 months for fuel prices on record.