September saw the end of three consecutive months of rising fuel costs, according to data released today.

According to RAC Fuel Watch, the average price of both petrol and diesel stayed the same during the month, remaining at 114p per litre for petrol and diesel at 118p a litre.

The average price of fuel sold at the four major supermarkets stands at 109p a litre for petrol and 114p for diesel. Despite this, motorway fuel prices rose with petrol jumping 2.57p a litre to an average of 126.72p across the UK. Diesel also spiked by 1.83p to 131.14p a litre.

Simon Williams, RAC fuel spokesman, said: “After three months of rising fuel prices drivers will be relieved to see the cost of both petrol and diesel staying the same. Since June when prices stopped falling as a result of the coronavirus movement restrictions being eased, the cost of fuel has been going up steadily.

“While price rises are never good news, they have not gone back to the high levels seen at the beginning of the year.”

With the average price of a litre of unleaded standing at 114p a litre, it means that filling up an average 55-litre tank will cost £63, or £7 less than it was in January. Diesel owners are paying £65 for a full tank, contrasting the start of the year when this would cost close to £73.

Yet according to the data diesel owners are overpaying for fuel by some margin. The wholesale price of diesel has been lower than petrol for six weeks, yet the average forecourt price for the former is still 3.5p more than the latter. Over the same period, the wholesale price of a litre of diesel has averaged at around 85p, compared with petrol’s 87p.

It means that diesel could be sold by the lowest cost retailers for in the region of 110p a litre, which would still take into account a 5p retailer margin.

Williams added: “Diesel drivers should feel short-changed by the decision of retailers to keep prices artificially high. The price of a litre is currently 8p higher than it should be due to reductions in the wholesale price.

“In fact, the wholesale price of diesel has now been lower than the petrol equivalent for six weeks, yet petrol continues to be sold for 3.5p less than diesel. This must surely be difficult for retailers to justify. We strongly urge them to lower their prices in an effort to restore drivers’ trust.