The simple answer is the BMW 330e PHEV, which has an official combined consumption figure of 313.9-353.1mpg, but as most people are already aware official figures do not necessarily reflect what you will achieve in the real world. If you have the ability to charge your car at home then a plug-in hybrid has the potential to give you the best mpg, particularly if you do frequent short journeys, as the more miles you can do on electric power the less fuel you will use. Our Real MPG guide shows that when comparing petrol, diesel, self-charging and plug-in hybrids, our readers have achieved the highest figures in PHEVs, with the Toyota Prius Plug-in achieving an average of 133.5mpg - www.honestjohn.co.uk/guides/economical-cars/best-m.../

This guide also shows that the best-performing petrol car was the Suzuki Celerio at 70.2mpg, the best diesel was the Nissan Micra at 69.6mpg and the best self-charging hybrid was the Toyota Yaris Cross at 70.5mpg, but it is important to consider what kind of car you need, and that the fuel economy you achieve will depend on the kind of journeys that you make and your driving style.