What Does MPG Mean in Cars?

MPG in plain English

Miles per gallon, or MPG, tells you how far a car travels on one UK gallon of fuel. In Great Britain that gallon is 4.546 litres, not the smaller US measure you might see online. If a car returns 50 MPG, it can cover 50 miles for every gallon you put in the tank. The higher the number, the more efficiently your fuel is being used.

Why it matters is simple: MPG shapes your monthly costs, your driving range between fill-ups, and your carbon footprint. The UK average sits around 38 MPG, with petrol models typically a little lower and diesels a touch higher. Hybrids often push beyond 60 MPG thanks to electric assistance and smart energy recovery. Newer cars benefit from tighter emissions rules and improved engines, so many exceed the historic average in real-world conditions.

You will see two kinds of MPG. Official figures come from the WLTP test - a global lab procedure designed to reflect urban, suburban, rural and motorway driving. These give a fair, comparable benchmark but your actual results will vary with road type, traffic, temperature, payload and your driving style. That is where real-world MPG comes in. You can calculate it yourself using your trip miles and the litres you add at the pump, then convert to UK gallons. Many modern dashboards also show live and trip-average MPG so you can see how a gentle right foot on the motorway typically beats stop-start city traffic.

Higher MPG means lower fuel bills and lower CO2.

A quick rule of thumb helps if you spot European figures in litres per 100 km: lower L/100 km is better, while higher MPG is better. You can convert by dividing 282.48 by MPG to get L/100 km, or dividing L/100 km by 2.825 to get MPG. That way, a 40 MPG car lines up at roughly 7.06 L/100 km, keeping comparisons consistent when you browse continental spec sheets or apps.

Who benefits from this guide

If you drive in the UK and want to cut running costs, understanding MPG will help you choose the right car and the right driving style. Commuters facing urban congestion can compare city-heavy MPG against motorway-friendly models, while long-distance drivers can see why diesel or efficient hybrids offer fewer fuel stops. First-time buyers can budget confidently, and experienced motorists can check whether real-world results match official WLTP figures. If you are considering a car on finance, clearer MPG expectations make monthly budgeting more accurate and help you weigh total cost of ownership.

Your choices at a glance

1. Prioritise high-MPG models - efficient petrol, diesel or hybrid options.

2. Compare WLTP urban, motorway and combined MPG before buying.

3. Calculate your real MPG using miles, litres and the UK gallon.

4. Adjust driving style - smooth acceleration, correct tyre pressures, lighter loads.

5. Consider hybrid for city routes or diesel for frequent long motorway trips.

6. Track MPG on your dashboard and with fill-to-fill logs.

7. Convert EU L/100 km figures for apples-to-apples comparisons in the UK.

Pounds, impact and practical trade-offs

Who can apply and what matters

Most UK drivers can use MPG comparisons to inform a purchase, but eligibility for the lowest running costs depends on your routes and habits. If your week is dominated by short, cold starts and urban traffic, expect lower MPG than the combined figure and look closely at WLTP urban results or consider a hybrid that thrives in stop-start conditions. If you routinely cover long motorway distances at steady speeds, diesel or highly efficient petrol models can deliver excellent MPG and range. Payload, roof boxes, big wheels and air conditioning all reduce efficiency, so consider the specification that matches your needs rather than the most eye-catching trim. If you plan to finance your car, Kandoo can connect you with a panel of lenders so you can balance the monthly payment against expected fuel spend and total cost of ownership.

Work it out in a few steps

1. Reset trip counter at fill-up and note odometer.

2. Drive normally until you next refuel.

3. Record miles driven since the last fill.

4. Note litres added to fill the tank.

5. Calculate: MPG = (miles ÷ litres) × 4.546.

6. Compare with WLTP urban, motorway and combined.

7. Adjust driving style and track improvements.

Trade-offs to weigh up

Read this before you pick a car

Official WLTP data is invaluable for like-for-like comparisons, but your routes matter more. Urban congestion, frequent short journeys and heavy loads pull MPG down. Motorway cruising with gentle inputs usually lifts it. Look beyond the headline combined figure and scan the low, medium, high and extra-high speed categories to match how you actually drive. If you see European L/100 km in brochures or apps, convert it so you are not comparing unlike-for-unlike. Finally, check tyre labels, servicing history and wheel size, all of which influence efficiency, and verify real MPG yourself with a couple of fill-to-fill calculations. Small habits add up, and reliable records make budgeting far more predictable.

Small setup changes and smoother driving can unlock meaningful MPG gains.

Next steps: shortlist three models, compare WLTP categories, then test drive on your real route.

Alternative routes to savings

1. Downsize engine or vehicle class for lower weight and drag.

2. Choose a plug-in hybrid or EV for shorter commutes and cheap off-peak charging.

3. Use car club or leasing if annual miles are low and predictability matters.

4. Optimise insurance, servicing plans and tyres to trim total cost of ownership.

Common questions, clear answers

Q: What exactly is MPG in the UK? A: It is miles travelled per UK gallon of fuel. One UK gallon equals 4.546 litres.

Q: What is a good MPG figure today? A: The UK average is around 38 MPG. Many newer petrol and diesel cars exceed this, while efficient hybrids can reach 60 MPG or more.

Q: Why is my real MPG lower than the brochure? A: WLTP is a lab test reflecting mixed driving. Real results vary with city traffic, weather, weight, tyres and your driving style.

Q: How do I calculate real MPG? A: After a fill-up, record miles driven and litres added next time. Use MPG = (miles ÷ litres) × 4.546.

Q: What is L/100 km and how do I convert it? A: It is Europe’s measure where lower is better. Convert by 282.48 ÷ MPG to get L/100 km or L/100 km ÷ 2.825 to get MPG.

Q: Which fuel type gets the best MPG? A: Diesel typically leads on long runs. Hybrids excel in urban driving. Petrol models vary widely by size and technology.

Q: Does motorway driving improve MPG? A: Usually yes. Steady speeds and fewer stops help, though very high speeds and strong headwinds reduce efficiency.

How Kandoo helps you move further for less

Kandoo is a UK-based retail finance broker that helps you find car finance to match your budget, credit profile and expected running costs. We pair lender options with practical fuel economy guidance, so you can balance the monthly payment with realistic MPG and total cost of ownership. Check your eligibility with no obligation and get a decision quickly.

Important information

This article provides general guidance only and is not financial advice. MPG and costs vary with vehicle condition and driving. Always verify figures with your own calculations and review full terms before taking out finance.