Diesel drivers are facing eyewatering 20p per mile charges this week following weeks and weeks of price increases at the pumps.

Despite recent news that the price of oil has dropped suddenly folowing the announcement of a potential two-week ceasefire in Iran, the price is not yet coming down at petrol stations, with the average price of a litre of diesel now reaching a staggering 189.42p a litre today (Wednesday April 8), according to the RAC. In January, the Express reported that diesel cost 142.96p per litre on average, which means the price has increased by 47p per litre since the start of 2026.

According to motoring and insurance website Nimblefins, the average fuel economy of UK diesel cars is 43mpg (though this can be lower for city-only driving), which means that, based on the current price per litre, it currently costs 20p per mile to run a diesel car, not including any other costs such as maintenance. In January, at the old prices, this would have been just 15p, 25% lower.

The increases follow the launch of the UK's new Fuel Finder last month, which allows drivers to see prices at all petrol stations near them in real time, and it is hoped it will save drivers £40 a year due to increased competition.

The Competition and Markets Authority (CMA) told firms responsible for thousands of fuel stations across the country that it was bringing forward formal requirements to supply revenue, costs and sales data.

The watchdog said the move would speed up its review of fuel margins made by businesses since the conflict began.

The CMA said it will also consider how quickly fuel prices rise and fall as wholesale costs change and whether there is evidence of so-called "rocket and feather" pricing.

While it recognised that businesses across the economy were likely to face significant pressures from rising energy costs which could affect prices, it said fuel stations "should not exploit the situation", adding that any evidence of this would be made clear in its update on pricing, "which will be published as soon as possible".

The CMA's executive director for markets, Juliette Enser, previously said: "Whilst price increases might be inevitable because of rising wholesale costs, it is important that those increases reflect genuine cost pressures.

"We will be closely scrutinising and reporting on what's happening with fuel prices and call out any concerning behaviour."

Petrol and diesel costs for motorists in the UK have risen sharply since Donald Trump launched his military action.

On Wednesday, London's FTSE 100 index of major firms jumped by as much as 2.6% at the start of trading on the back of the ceasefire announcement.

The price of benchmark Brent crude oil slid by 14.3% to 93.6 US dollars (£69.78) a barrel, although this was still well above the price of around 70 dollars at the start of the conflict.

Mr Trump had warned on Tuesday that "a whole civilisation will die" unless Tehran met his demands.

But less than two hours before his deadline passed for Iran to agree a deal, the US president said he was suspending his threat to widen the military offensive to power plants and bridges, subject to the Strait of Hormuz reopening.

Sir Keir said: "I welcome the ceasefire agreement reached overnight, which will bring a moment of relief to the region and the world.

"Together with our partners we must do all we can to support and sustain this ceasefire, turn it into a lasting agreement and reopen the Strait of Hormuz."