Fuel prices are once again a major part of the car-buying decision. RAC Fuel Watch data published on 2 October 2026 shows the average UK price of diesel reached 200.01p per litre, crossing the £2 threshold for the first time on average.
According to the RAC, filling a 55-litre diesel tank now costs about £110.01. A comparable tank of petrol costs around £96.09. The organisation links the latest increase to disruption in global fuel markets and the ongoing conflict in the Middle East.
Does this mean diesel no longer makes sense?
Not necessarily. Diesel can still suit drivers covering high annual mileage, especially regular motorway journeys where an efficient diesel can return strong fuel economy. The problem is that the calculation has changed as pump prices have risen.
A buyer doing 5,000 miles a year has a very different cost profile from somebody doing 20,000 miles. Instead of choosing a fuel type based on old assumptions, it is worth estimating your own annual mileage and comparing realistic fuel consumption.
Compare the total cost, not just the pump price
Fuel is only one part of ownership. A cheaper petrol car might use more fuel. An electric car can be inexpensive to charge at home but less attractive for somebody relying heavily on rapid public charging. A hybrid can work well for mixed use, but only if the vehicle and driving pattern suit each other.
When comparing used cars, consider:
- purchase price and depreciation
- annual mileage
- real-world MPG or energy consumption
- insurance
- vehicle tax
- servicing and repair costs
- where you normally refuel or recharge
Higher diesel prices may influence used demand
Autotrader data released at the end of September also indicated that buyer interest was shifting. Among used cars up to five years old, electric cars increased their share of enquiries while diesel's share fell during September. That does not mean demand for every diesel will disappear, but it shows running costs are increasingly affecting buyer behaviour.
For sellers, the best response is accuracy. If a diesel has strong fuel economy, full service history and is well suited to long-distance use, make those strengths clear. Buyers still value the right car for the right job.
What should buyers do now?
Work backwards from your own driving. If most journeys are short and local, a diesel may no longer be the obvious choice. If you spend hours each week on the motorway, a good diesel can still be competitive despite higher fuel prices.
The latest fuel-price figures are available from RAC Fuel Watch.
You can compare petrol, diesel, hybrid and electric used cars at Motavo.
