Diesel cars can still cost less to run than petrol despite record pump prices, says Which?

Pump prices hit record highs

Fuel prices at UK forecourts have reached record levels, with average prices on 5 October standing at 174.7p a litre for petrol and 200p a litre for diesel, according to analysis by Which?. Despite diesel commanding a 25.3p a litre premium over petrol, the consumer group found that diesel cars can still work out cheaper to run overall for many drivers.

The numbers behind the running costs

Which? calculated running costs for a driver covering around 6,000 miles a year. Using these figures, a diesel Volkswagen Golf costs roughly £115 a year less to fuel than the equivalent petrol model, even with diesel priced higher at the pump. The diesel version would only become the more expensive option to run if diesel prices rose to 228p a litre while petrol remained at 174p a litre, Which? said.

The saving reflects the better fuel economy diesel engines typically achieve compared with petrol equivalents, which can offset the higher cost per litre over a year of driving.

Diesel’s fall from favour

Diesel cars were once actively encouraged by successive UK governments, and uptake followed suit. Nearly a third of new cars registered in the UK in 2004 were diesel, rising to more than half of all new car registrations by 2011. That popularity has since collapsed. Diesel now accounts for just 4% of new cars registered in the UK.

Land Rover leads the diesel market

Despite diesel’s overall decline, one brand continues to rely heavily on it. Land Rover is the only UK car brand that registers more diesel cars than any other fuel type, despite also selling petrol and petrol plug-in hybrid models. In September 2026, around 1.5% of all new cars registered in the UK were diesel Land Rovers, and the brand accounted for more than 40% of all diesel car registrations that month.

Volkswagen, as the UK’s bestselling car brand overall, is one of the few other manufacturers, alongside Audi, that still sells significant numbers of diesel cars.

Emissions and engine quality

Which? noted that diesel engine technology and emissions performance have improved considerably over the past decade, even as electric vehicles remain the cleaner option on the road. Dino Buratti, a senior researcher at Which?, said diesel cars offer strong pulling power rivalled only by electric cars, and praised the smoothness of larger six-cylinder diesel engines found in vehicles from Mazda, Land Rover and BMW, describing some as “surprisingly quiet” to drive.

What happens next

With pump prices for both fuels remaining at record levels, the relative running costs of petrol and diesel vehicles will continue to depend on how prices for each fuel move in the months ahead. Which? said its comparison was based on prices recorded on 5 October, and the gap between diesel and petrol running costs could narrow or widen if that price differential changes.