Petrol & Diesel Cost Per Mile UK (2025/26 Running Costs Guide)

UK motoring costs guide · Last updated 2026 · Data: RAC Fuel Watch & HMRC

Petrol and diesel prices in the UK may have settled well below the record highs of 2022, but fuel is still one of the biggest monthly bills most drivers face. Whether you commute twenty miles a day, run a small business from your car, or are simply trying to budget for the school run, knowing your true cost per mile is the single most useful number you can calculate. It tells you what every journey really costs, lets you compare petrol, diesel and electric cars on a like-for-like basis, and helps you decide whether trading to a more efficient car would actually pay for itself.

This guide explains exactly how to work out your cost per mile, what 2025's average UK fuel prices mean for real drivers, how HMRC mileage claims work, and how petrol, diesel and EVs stack up against each other in 2025/26. If you already know your car's mpg and today's fuel price, jump straight to our UK Petrol Cost Calculator for an instant answer — or keep reading for the full running costs picture.

2025/26 fuel prices in the UK: what are you paying per litre?

According to RAC Fuel Watch, the average price of unleaded petrol across the UK was around 161 pence per litre for much of 2025, while diesel averaged close to 182 pence per litre. To put that in context, filling a typical 50-litre tank costs roughly £80 for petrol and £91 for diesel. Prices vary noticeably by region and by forecourt: supermarket stations are usually 3–6p cheaper than motorway services, Northern Ireland has tended to see the lowest regional averages, and remote rural areas regularly pay the most per litre.

The gap between petrol and diesel — the so-called "diesel premium" — has narrowed since the price spikes of 2022, but diesel still typically costs around 20p more per litre. That does not automatically mean diesel is more expensive to drive, however: diesel engines are generally 10–20% more fuel efficient than equivalent petrol engines, so the higher pump price can be more than offset by better fuel economy. We compare the two in detail later in this guide.

How to calculate your car's cost per mile

The maths is simple once you convert miles per gallon (mpg) into litres per mile. UK cars measure fuel economy in miles per imperial gallon, but fuel is sold in litres — and one imperial gallon contains 4.546 litres. So: litres per mile = 4.546 ÷ mpg, and cost per mile = litres per mile × price per litre. The example box below runs the numbers for the most common scenario: a petrol hatchback averaging 45 mpg.

For a driver covering 10,000 miles a year in a petrol car averaging 45 mpg, that adds up to roughly £800–£900 in fuel over the year at 161p per litre — a figure worth comparing against your own annual mileage. If you would rather not do the arithmetic yourself, the fastest way to get an exact figure is our UK Petrol Cost Calculator — enter your mpg, annual mileage and today's pump price and it does the conversion for you.

Typical fuel economy: what mpg should you expect?

Real-world mpg varies enormously with car size, engine, and how you drive, but the following ranges are a reliable rule of thumb for 2025-era cars:

• Small city cars (VW up!, Toyota Aygo, Fiat 500 class): 45–55 mpg in mixed driving.
• Family hatchbacks (VW Golf, Ford Focus, Vauxhall Astra class): 40–50 mpg for petrol; diesel versions often manage 10–15 mpg more.
• SUVs and crossovers (Nissan Qashqai, Kia Sportage, Land Rover Defender class): 25–35 mpg, with large petrol SUVs dipping below 25 mpg in town.

Hybrids change the picture considerably: a self-charging hybrid such as the Toyota Yaris Hybrid can exceed 60 mpg in urban driving, while a plug-in hybrid's real-world economy depends almost entirely on how often you actually charge it. Official WLTP figures are usually optimistic — expect real-world economy to be 10–20% lower, especially in winter or heavy traffic.

Cost per mile: petrol vs diesel vs EV (2025/26)

The table below compares representative vehicles at 2025 average prices: petrol at 161p/l, diesel at 182p/l, and home electricity at roughly 25p/kWh assuming a typical EV efficiency of around 3.5 miles per kWh. Costs are rounded and assume steady, mixed driving.

A few things stand out. Electric cars are dramatically cheaper to run when charged at home — roughly 6–9p per mile, a fraction of any petrol or diesel figure — but public rapid charging at 60–80p/kWh pushes an EV's cost per mile to around 20p, close to a petrol hatchback. Among combustion cars, diesel beats petrol per mile whenever its economy advantage exceeds the price gap; in practice, motorway-heavy drivers usually do better in a diesel, while urban stop-start driving often suits a small petrol, hybrid or EV.

Petrol vs diesel per mile at common mpg figures

Because diesel costs more per litre but tends to be more efficient, the fairest comparison is side by side at matching mpg. At 2025 prices a diesel needs roughly a 13% mpg advantage to break even with petrol (182 ÷ 161 = 1.13). The table below shows the cost per mile for both fuels at common economy figures:

Read the table this way: at equal mpg, petrol is always cheaper per mile — the question is whether your diesel's real-world economy is enough higher to compensate. A petrol hatchback averaging 45 mpg costs about 16.3p per mile; a diesel hatchback that genuinely manages 60 mpg costs about 13.8p per mile — a saving of roughly £250 a year at 10,000 miles, before you factor in the higher upfront cost of most diesel cars.

How HMRC mileage claims work (2025/26)

If you use your own car for work, you can claim tax relief on business mileage using HMRC's Approved Mileage Allowance Payments (AMAP) rates. For 2025/26 the rate is 45p per mile for the first 10,000 business miles in a tax year, and 25p per mile for every mile after that. The 45p figure is not just fuel — it is designed to cover fuel, insurance, tax, MOT, servicing, tyres and depreciation. If your employer pays you less than 45p per mile, you can claim tax relief on the difference; if they pay more, the excess is treated as taxable income.

There is a separate set of figures — the Advisory Fuel Rates — for employees who drive a company car and are reimbursed for fuel. These are banded by engine size and fuel type, and HMRC updates them every quarter (March, June, September and December) to track pump prices. The current banding structure looks like this:

Because advisory fuel rates change quarterly, always check HMRC's current table before submitting a claim. Whichever scheme you use, keep a proper mileage log — dates, journey purpose and miles — because HMRC can ask to see your records, and a well-kept log is also the basis for accurate cost-per-mile calculations of your own.

What changes your cost per mile?

Pump prices and official mpg figures only take you so far. In the real world, the following factors can move your actual cost per mile by several pence in either direction:

Driving style

Hard acceleration and heavy braking can increase fuel consumption by 10–30%. Smooth, steady driving — reading the road ahead and easing off early — is the cheapest "modification" you can make. On the motorway, dropping from 80 mph to 70 mph saves a meaningful amount of fuel, and most petrol and diesel cars are at their most efficient around 50–60 mph in a high gear.

Traffic and idling

Stop-start traffic is brutal on economy because idling burns fuel without moving you anywhere. Modern start-stop systems help, but avoiding rush hour, planning routes and switching the engine off when parked for more than a minute or so all cut waste. Cold engines also use noticeably more fuel — short winter journeys can be 20–30% thirstier than the official figure.

Tyres

Under-inflated tyres increase rolling resistance, so checking pressures monthly — and before long trips — can save roughly 2–3% of your fuel bill while improving safety. Wide, soft-compound performance tyres cost more in fuel than standard touring tyres, and winter tyres are slightly thirstier than summer tyres in warm weather.

Air conditioning and electrics

Air conditioning can add roughly 5–10% to fuel use in town. At motorway speeds it is more efficient to close the windows and use the AC than to drive with windows open, which creates significant aerodynamic drag. Demisters, heated seats and heated screens all draw from the alternator and add engine load, so use them sparingly.

Weight and roof racks

Every extra 50 kg — a roof box, a boot full of luggage — increases fuel use. Roof boxes and empty roof bars are actually worse than raw weight because they wreck aerodynamics; remove them when they are not needed and you will see the difference on the motorway.

Frequently asked questions

Related guides

Related tools