Motoring experts have warned drivers who fill up with diesel are paying more at the pumps than they rightly should be.
According to the RAC, diesel drivers are "paying a huge premium" compared to those who have unleaded cars, although there is currently little difference between the two fuels on the wholesale market.
If you are one of the 12million people who drive diesel cars you will pay 20p more than someone filling up a petrol car at the pumps, warns the firm. However, RAC claims there's just one place drivers can find a better deal - Costco.
The wholesale price of diesel was 121.06p last week - just 6p more than petrol which was 115.48p. Even so, diesel drivers have to pay 168p a litre, compared to 148p for unleaded.
The RAC calculates that if diesel was being sold at a fairer rate drivers would be paying no more than around 155p per litre, saving a motorist £7 when filling up an average 55-litre family car.
RAC fuel spokesman Simon Williams says only Costco has slashed the price of diesel this week - by a "massive" 4p reduction per litre.
He said: "While our data shows petrol is generally being sold at a fair price at forecourts at the moment, drivers of the country's 12m 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.
"The fact membership-only retailer 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."
The RAC is calling on retailers to urgently cut the price of diesel to fairer levels, following the lead of Costco as retailers are currently taking more than double the margin on every litre of diesel.
"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," Simon adds. "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."
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