Figures from data firm Experian show the average price of a litre of diesel at UK forecourts reached a new high of 197.1p on Tuesday.
RAC fuel spokesman Simon Williams said wholesale costs mean pump prices are "on course" to hit 200p per litre, as reports suggest car use increased 80 per cent on Tuesday due to the rail strike.
Mr Williams said the price of diesel is "perilously close to the £2-a-litre milestone", with the cost of a full tank for a 55-litre family car exceeding £108.
He went on: “With the oil price falling and wholesale costs down over the last week, pressure is mounting on the biggest retailers to turn the tide and put petrol pump prices into reverse.
"It now seems we’ve reached the current petrol peak, so we expect to see the big four supermarkets start to cut their prices.
"As they dominate UK fuel retailing this should lead to others reducing their prices too, which will benefit drivers everywhere.
"The situation with diesel is different, unfortunately, as wholesale prices last week still put it on course to move closer towards an average of £2 a litre."
We checked out petrolprices.com to see what the cheapest prices were in the Black Country.
Here are the best prices we found on Wednesday morning:
Blakenhall service station, Dudley Road: 181.6p
Tesco Esso, Moss Grove, Kingswinford: 182.9p
Tesco Esso, Hagley Road, Stourbridge: 182.9p
Asda, The Boulevard, Dudley: 183.7p
Asda, Avon Road, Cannock: 183.7p
Blakenhall service station, Dudley Road: 190.6p
Morrisons, Market Street, Bilston: 192.7p
Asda, Avon Road, Cannock: 192.7p
Asda, Jack Haywood Way, Wolverhampton: 193.7p
Sainsbury's, Kenmare Way, Wednesfield: 194.9p