Petrol vs diesel: which is cheaper to run in 2026?
Pump prices, cost per mile, tax, maintenance and resale, with the numbers worked through.
Key points
- In late September 2026, diesel averaged 191.1p a litre against 158.9p for unleaded: a 32p gap.
- Diesel's better mpg barely offsets that gap: per mile, the two are now close.
- Petrol wins on insurance, maintenance, resale and clean air zones, so it's the cheaper choice for most drivers.
At the pump
Across around 7,500 UK stations in late September 2026, E10 unleaded averaged 158.9p a litre and B7 diesel 191.1p. A 55-litre fill of diesel cost about £17.70 more.
Cost per mile
Diesel engines are more efficient, typically returning 15–20% more miles per gallon than the equivalent petrol. At current prices, that advantage is almost used up by the higher price per litre.
| Petrol (E10) | Diesel (B7) | |
|---|---|---|
| Average price | 158.9p/l | 191.1p/l |
| Example economy | 45 mpg | 55 mpg |
| Fuel cost per mile | 16.1p | 15.8p |
| Fuel for 10,000 miles | £1,605 | £1,580 |
A saving of about £25 a year on fuel is easily wiped out by diesel's other costs.
Insurance
Diesels often cost a little more to insure because of higher list prices and repair costs. Shopping around matters far more than fuel type.
Road tax (VED)
Most cars registered since April 2017 pay the same flat standard rate whether petrol or diesel. Diesels that don't meet the RDE2 emissions standard pay a higher first-year rate. Check the current rates on GOV.UK before you buy.
Maintenance
Diesels carry extra costs petrol cars avoid:
- Diesel particulate filter (DPF): short trips stop it cleaning itself; a replacement can run to four figures.
- AdBlue: most modern diesels need regular top-ups.
- Turbo and injectors: hard-working parts that can be expensive to replace.
Resale value
Demand for used diesels has fallen since 2018. Smaller petrol cars generally hold their value better; diesel residuals are strongest for large SUVs and vans.
Clean air zones and ULEZ
London's ULEZ covers all of Greater London, and several other cities run clean air zones. Diesels generally need to meet Euro 6 (most registered from September 2015); petrol cars only need Euro 4 (most from 2006). If you drive into these zones, an older diesel is a bigger risk.
Which should you choose?
Petrol, if you
- drive under 15,000 miles a year
- do mostly short or urban trips
- drive into clean air zones
- want lower maintenance and better resale
Diesel, if you
- cover very high motorway mileage
- tow a caravan or trailer
- need a large SUV or van where diesel is far more efficient
The bottom line
With diesel about 32p a litre dearer, petrol is the cheaper choice for most UK drivers in 2026. Whichever you run, where you fill up still matters: compare petrol prices or diesel prices near you, and see 10 ways to save money on fuel.
Questions
Is diesel cheaper per mile than petrol?
Only slightly at late-September 2026 prices. A 55 mpg diesel costs about 15.8p a mile against 16.1p for a 45 mpg petrol car, because diesel is about 32p a litre dearer.
Who should still buy a diesel?
Drivers covering very high motorway mileage or towing heavy loads. For most other drivers, petrol is cheaper overall.