The biggest gap between petrol and diesel pump prices since at least 2000 has emerged this week, resulting in increased costs for diesel drivers.

Diesel is now a record 17p a litre more expensive than unleaded, according to the RAC

While average prices of both petrol and diesel have dropped considerably from the all-time highs of the summer, diesel is now a record 17p a litre more expensive than unleaded, according to the RAC. Its data reveals a UK-wide average of 180.22p for the former compared to an average of 162.96p for petrol.

The gap between the two fuels is normally around 4p a litre but this has widened since Russia invaded Ukraine. Prior to this, the gap had last hit an 11p high back in August 2015.

On the wholesale market, the disparity is currently 20p a litre but has been as high as 27p at the end of August this year. Despite this, the gap at the pumps in the following fortnight – the time it generally takes for price changes on the wholesale market to be fully reflected on the UK’s forecourts – only averaged 14p.

RAC fuel spokesman Simon Williams said several factors were combining to make diesel more expensive.

“While the EU is not set to ban Russian diesel imports until February 2023, the UK has already done so. This is significant as we used to import a third of our diesel from Russia.

“In addition, European demand for gas oil – red diesel – tends to go up at this time of year as it is commonly used for heating. And this is greater this autumn as Europe is looking to lessen its reliance on gas and, as a result, is boosting its diesel supplies to get through the winter.”

All of which means it continues to be a tough time to be a diesel driver.

“Fortunately, the average price is now almost 20p a litre less than it was at its high of 199.09p in late June,” Williams added. “But with the pound recently dropping to record lows against the dollar, all we would need is for the price of oil to start rising from its current level of around $90 a barrel to cause both diesel and petrol prices to climb back up again.”

RAC data also reveals times when diesel has been sold for less than petrol – the biggest gap was 3p in August 2015 when petrol averaged 114p and diesel 111p.