Fleets face further price rises after a record-breaking week at the pumps.
Petrol hit a new high on December 9 at 121.76 pence per litre (ppl), beating the record of 121.61ppl set in May.
Diesel rose by 1.6p to 125.73ppl, up 14.21p on the start of the year.
The new figures have added £5.94 to a 50-litre tank of petrol and £7.11 to a tank of diesel compared to a year ago, according to the AA.
Despite these increases, the latest Advisory Fuel Rates from HMRC have fallen by a penny, to 15p per mile (ppm), for diesel cars with an engine size above 2.0 litres. The figures are based on an applied average of 37.3mpg. Drivers of more efficient cars will be overpaid; those of less efficient cars will lose out.
Rates have risen by 1ppm for petrol cars of 1.4 litres or less (13ppm) and for diesels up to 2.0 litres (12ppm).
However, analysis of official fuel figures suggests the AFRs, based on 122.7ppl diesel prices, are overly generous (see table).
Even if drivers are typically achieving 10% below manufacturers? official figures, they will still be paid too much by their company under the AFRs.
Tesco could overtake BP to become Britain?s biggest petrol retailer thanks to its investment in Greenergy. The road fuel supplier is understood to be interested in buying more than 700 petrol stations in the UK from French oil group Total and 460 from Murco.
Both companies have put their UK retail chains up for sale to focus on oil and gas production.