Diesel fell by 2 pence in May, falling below 139p per litre (ppl) for the first time since September 2021, according to new analysis from the RAC.

Diesel dropped from 140.5p to 138.4p, while petrol also came down by 2p, from 134p at the start of May to 132.3p by the close – the lowest price for petrol since early July 2021.

The 2p-a-litre drop in both fuels means another £1 was shaved off the cost of filling a 55-litre family car last month (May).

A full petrol fill-up is now £72.74 while diesel is £76.13. This means unleaded has come down by more than 7p since the end of February (139.65p) and diesel by 8p (146.5p), saving drivers around £4 a tank.

A litre of supermarket unleaded is now down to 129p and diesel to 135p, both 3p lower than the UK averages.

In Northern Ireland, however, the average price a driver pays for a litre of petrol is even lower at 126.5p – nearly 6p cheaper than the UK average. Diesel is 130.8p – nearly 8p cheaper than the average UK price.

Sainsbury’s Shorehead store at Southgate in Huddersfield currently has some of the lowest pump prices, with a litre of petrol just 121.9p.

Asda’s forecourt on Western Road in Park Royal, London, is not far off at 122.7p, while Tesco is pricing at 123.9p less than three miles away at Western Avenue in Greenford.

The cheapest supermarket diesel on sale is at Sainsbury’s in Falls Road, Belfast, at 126.9p.

Asda is not far behind, offering diesel at 127.7p at two Northern Ireland locations – Coleraine and Cookstown, and at Breck Road in Liverpool. Sainsbury’s Southgate in Huddersfield is 129.9p.

RAC head of policy Simon Williams said: “May was another good month at the pumps for drivers as petrol and diesel fell by 2p a litre, making for three straight months of falling prices.

“While this takes us back to prices last seen almost four years ago, it’s worth remembering that prices are lower today because the 5p duty cut, first introduced in March 2022, is still being applied.

“If it wasn’t for the fuel duty freeze, prices could well be much higher.”

With oil averaging $64 a barrel throughout May, the RAC believes the average price of petrol ought to be under 130p and diesel under 134p.

“Hopefully retailers will continue to reduce their prices, so we see four months of falling costs at the pumps at the end of June,” concluded Williams.