You should find that almost any small petrol car will be capable of completing a 400 mile journey on a single tank. For example, the Skoda Fabia has a tank capacity of 45 litres, and a steady 70mph should comfortably see you achieving 50mpg if not more, which would get you 494 miles on a single tank.

However, if you want even more range we would suggest considering the cars that achieved the best results in our Real MPG guide that you can see here - www.honestjohn.co.uk/guides/best-mpg-cars/. The Suzuki Celerio achieved a Real MPG figure of 70.2mpg, and with a 35 litre fuel tank would get you 539 miles on a full tank.