MPG Check: What MPG Does My Car Do?

An mpg check tells you how many miles a car should travel on a gallon of fuel, which is the biggest single running cost after depreciation. Enter the registration in the search box above: the free check shows the car's fuel type, engine size and CO2 figure from the DVLA record, and from the CO2 figure you can work out an approximate mpg with the table on this page. The full report shows the manufacturer's own fuel economy figures for that exact car where they are recorded: urban, extra-urban and combined mpg, alongside the full specification and the history checks that matter when buying.

What mpg is my car?

There are three answers, and it pays to know which one you are looking at:

• The manufacturer's official figure, measured in a laboratory test. It is the figure in adverts and brochures, and the one the full report shows where it is recorded for the car. Since the switch to the WLTP test (new models from September 2017, all new cars from September 2018) the figures are closer to real driving; the older NEDC figures on cars before that were often 20 to 30% higher than owners achieved.
• An estimate from the CO2 figure. Fuel burned and CO2 produced are tied together, so the CO2 g/km on the DVLA record converts to a rough mpg. This is the free route, and it is good enough to compare two cars.
• Your real-world figure, measured from the pump, which depends on how and where you drive. Usually the lowest of the three.

For a quick like-for-like comparison, use the official or CO2-based figure; for a budget, measure the real one.

Check your car's mpg by reg

1. Run the free check above. The result shows the fuel type, engine size and CO2 g/km from the DVLA record, with our running-costs estimate.
2. Convert the CO2 figure with the table below, or the formula: petrol mpg is roughly 6,760 divided by the CO2 figure, diesel mpg roughly 7,440 divided by it. A 120 g/km petrol car works out at about 56 mpg; a 120 g/km diesel at about 62 mpg.
3. Want the manufacturer's figures? The full car history check includes the fuel economy section, with the urban, extra-urban and combined mpg and the full specification, where they are held for the car. The sample report shows where it sits.

Cars registered before March 2001 and some imports have no CO2 figure on the record, so the conversion will not work for them; the manufacturer's figures in the full report, or the handbook, are the fallback. Note that the two conversions are rough: they assume a typical petrol or diesel blend and the same test cycle behind both figures, and they are not meant for hybrids, which produce far less CO2 per mile than a plain petrol of the same mpg.

CO2 to mpg conversion table

Approximations from the carbon content of standard UK pump fuel (about 6,760 g of CO2 per gallon of petrol and 7,440 per gallon of diesel), rounded. They describe the test-cycle figure, not what you will get on your commute. Tax bands are for cars registered March 2001 to March 2017; see the car tax band check.

Mpg, litres per 100 km and UK versus US gallons

UK mpg uses the imperial gallon (4.546 litres). A US gallon is smaller (3.785 litres), so a US mpg figure for the same car is about 17% lower; do not compare a UK figure with an American review. Most of Europe quotes litres per 100 km instead, and the conversion is: UK mpg = 282.48 divided by l/100km. So 5 l/100km is 56.5 mpg, 6 l/100km is 47.1 mpg, 8 l/100km is 35.3 mpg and 10 l/100km is 28.2 mpg. The same formula works in reverse: l/100km = 282.48 divided by mpg.

Where the official figure comes from: WLTP and NEDC

Every new car is tested on a rolling road to a fixed cycle before it can be sold, and the mpg and CO2 figures from that test are what the DVLA records and what the manufacturer quotes. Two cycles have been used:

• NEDC (up to 2017/18): a short, gentle cycle with long steady-speed sections. Easy to optimise for, which is why the brochure figures of that era were hard to match on the road.
• WLTP (new types from September 2017, all new cars from September 2018): longer, faster, with more acceleration and the car's actual options and tyres taken into account. Figures fell by roughly a fifth on the same car, and are a far better guide.

Fuel consumption check: how to measure your real mpg

The brim-to-brim method is the one that cannot lie:

1. Fill the tank until the pump clicks off, and note the mileage (or reset the trip).
2. Drive normally for at least a full tank, ideally two or three.
3. Fill up again at the same pump, to the first click, and note the litres and the miles covered.
4. Divide the miles by the litres, then multiply by 4.546. 400 miles on 40 litres is 45.5 mpg.

The car's trip computer is handy but typically reads a few per cent optimistic, so check it against the pump at least once.

What affects the mpg you actually get

• Journey type: short, cold trips are the worst; a diesel may not warm up at all in two miles. A steady 50 to 60 mph is the best.
• Driving style: hard acceleration and late braking cost the most. Reading the road ahead and lifting off early saves more than any gadget.
• Speed: air resistance climbs sharply above 60 mph; 80 mph can use a quarter more fuel than 70.
• Tyres: under-inflated tyres add rolling resistance; check pressures monthly and after loading the car.
• Weight and drag: roof boxes, bike racks, a boot full of kit and open windows at speed all count.
• Condition: old spark plugs, a clogged air filter, dragging brakes or a lazy sensor can quietly take 10% off. A car whose MOT history shows emissions advisories is worth a closer look; the MOT history check is free.

Mpg and running costs

Mpg turns into pounds quickly. At 10,000 miles a year, a 40 mpg car uses 250 gallons (about 1,136 litres), and a 50 mpg car 200 gallons (about 909 litres): a difference of over 200 litres of fuel every year, for the life of the car. The fuel cost calculator works out the annual cost from any mpg, mileage and price per litre, and the car running costs check estimates fuel, tax and MOT costs for a specific reg. Vehicle tax rides on the same CO2 figure, so a low-mpg car is usually also a high-tax car.

When you are choosing between two used cars, the mpg difference is worth a few hundred pounds a year; a hidden finance agreement or an undisclosed write-off is worth the whole car. Of the cars our customers checked in full between March 2023 and October 2026, 30.1% had at least one risk record: finance, a write-off, a stolen marker, a scrapping record or a mileage anomaly. Run the full car history check before you pay for either.

Mpg check FAQs