How we test cars How we test mpg
Ever strived to match the manufacturer's claimed mpg figures in your car and not been able to? That's because the official numbers doesn't reflect everyday driving scenarios. Our real-world mpg test does, and that makes it a more accurate measurement.
Which? offers the most accurate and realistic real-world mpg figures
Manufacturers' mpg claims
Every new car launched is now available with manufacturer claimed mpg (miles per gallon) figures.
These are split into three different categories: Urban, signifying use in towns and cities; Extra Urban, referring to outside of towns and cities; and Combined, which merges the two previous together to give an overall average.
These measurements are taken from the EC test, carried out in a lab to simulate a mix of different types of driving.
What's the problem with EC mpg measurements?
Now that car tax rates in Europe are based on CO2 emissions, manufacturers are optimising their engines to emit the lowest CO2 in the test.
The introduction of modern, adaptable driver settings also means the EC test is conducted in the most efficient mode, which in many cases is not the setting owners will use in the real world due to restricted power and throttle response.
While the Urban test is carried out with a cold engine, the Extra-Urban test is conducted on the rolling road directly afterwards with a warm engine. And there is no test carried out under motorway speeds.
Our test replicates a more accurate impression of UK driving habits
How the Which? Car mpg test differs
The Which? Car test is a more accurate representation of how cars are driven in the UK.
Like the EC test, the Which? Car test is carried out on a rolling road in a our lab to make sure it is directly comparable for all cars we put through the cycle. We also test any cars with adaptable settings in the default mode the car starts up in without the driver making a selection.
And, unlike the EC test, our Urban and Extra-Urban test is conducted from both a cold and warm start and then averaged.
But our test also incorporates a section of motorway-style driving, at speeds up to 81mph (replicating speed limits of some European motorways).
Our Combined mpg figure is a combination of the Urban and Extra-Urban test together with the Motorway test, weighted 70:30.
We use a rolling road so all our tests are comparable
Real-world mpg figures for UK motorists
Our results therefore present much more realistic and achievable figures for UK drivers, and these are published in all our car online car reviews.
This gives you the opportunity to see and understand the mpg you can really expect to achieve from a specific model before purchasing. And it also provides more accurate figures for you to calculate your motoring costs.
More real-world mpg tests and results than anyone else
While many of our rivals only use claimed mpg figures in their car reviews, and some now offer a limited number of real-world figures, Which? Car has real-world mpg results for more than 1,600 models. Each one is the result of our in-depth mpg testing.
