At April 2026 UK pump prices, driving 100 miles in a diesel car costs between £14.47 and £28.95. The exact figure depends on your vehicle's MPG. Diesel sits at around 191p per litre, up from 166p in February 2026 after the March supply disruption.
100 Miles Diesel Cost by MPG (April 2026)
Diesel pump price: 191p per litre. Imperial gallon conversion: 4.546 litres per gallon.
| Vehicle | MPG | Cost for 100 Miles | Cost per Mile |
|---|---|---|---|
| Efficient diesel hatch | 60 | £14.47 | 14.5p |
| Modern saloon | 55 | £15.79 | 15.8p |
| Saloon / estate | 50 | £17.37 | 17.4p |
| Mid-size SUV | 45 | £19.30 | 19.3p |
| Large SUV / pickup | 40 | £21.71 | 21.7p |
| Van / older diesel | 35 | £24.81 | 24.8p |
| Heavy van / 4x4 | 30 | £28.95 | 29.0p |
Key takeaway: A modern 50 MPG diesel saloon costs £17.37 for 100 miles at current UK prices. The same journey in a 30 MPG van costs £28.95, an £11.58 difference per 100 miles. Across 7,400 miles per year (UK average) that gap widens to £856.
How the Calculation Works
The formula uses imperial gallons because UK MPG figures are quoted in imperial, not US, gallons:
Cost = (Distance / MPG) x 4.546 x Price per litre
For 100 miles at 50 MPG with diesel at 191p:
(100 / 50) x 4.546 x 1.91 = £17.37
For 100 miles at 40 MPG with diesel at 191p:
(100 / 40) x 4.546 x 1.91 = £21.71
Why Diesel Is More Expensive Than Petrol Per Litre
Diesel currently sits 33p per litre above petrol in the UK (191p vs 158p). This is unusual. Historically diesel was a few pence below petrol or roughly level. The gap opened in March 2026 after supply disruption from strikes on Iran cut diesel imports into Europe. Wholesale prices spiked, pump prices followed, and the gap has not closed since.
Diesel engines are still 15-20% more efficient per litre than equivalent petrol engines, which is what makes diesel competitive on cost per mile despite the higher pump price. But the per-litre premium has narrowed diesel's per-mile advantage to almost nothing for drivers swapping like-for-like.
Diesel vs Petrol vs EV for 100 Miles
Comparing diesel against the alternatives at typical efficiencies:
| Vehicle | Efficiency | Cost for 100 Miles |
|---|---|---|
| Diesel saloon | 50 MPG | £17.37 |
| Petrol saloon | 50 MPG | £14.37 |
| Petrol average | 40 MPG | £17.96 |
| EV (home, standard tariff) | 3.5 mi/kWh | £6.86 |
| EV (home, off-peak tariff) | 3.5 mi/kWh | £2.86 |
| EV (public rapid charger) | 3.5 mi/kWh | £14.29 |
An EV charged at home on an off-peak tariff costs roughly one-sixth of an equivalent diesel for 100 miles. A diesel only beats petrol when the diesel is meaningfully more efficient. A 50 MPG diesel against a 40 MPG petrol is genuinely cheaper per mile. A 40 MPG diesel against a 50 MPG petrol is not.
Annual Diesel Cost (7,400 Miles)
The average UK driver covers 7,400 miles per year. At 191p per litre:
| MPG | Annual Diesel Cost |
|---|---|
| 60 MPG | £1,071 |
| 50 MPG | £1,285 |
| 40 MPG | £1,606 |
| 30 MPG | £2,142 |
Fuel Duty Changes Coming
The current 5p per litre fuel duty cut ends 31 August 2026. After that, duty rises in three stages: +1p in September, +2p in December, +2p in March 2027. By March 2027 a 100 mile journey in a 50 MPG diesel will cost roughly 50p more than today. Read our fuel duty changes guide for the full schedule.
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