Driving your car Driver tools
Want to work out your car's true mpg, or whether you'll be better off with a diesel car? Our interactive tools make doing the sums easy.
How efficient is your car? Use our fuel calculator to check your mpg
Which is cheaper to run? We do the sums so you don't have to
Convert quickly and easily between bhp, kW and PS.
Quick litres-to-gallons conversion tool from Which?.
Free speed calculator tool
In our realistic tests, 95% of diesel cars, and 10% of petrol cars, pump out more NOx than limits allow. The majority of petrol cars we’ve tested also exceed carbon monoxide (CO) regulations, and some hybrid cars are not as innocent as claimed.