Subaru is using a new 'Boxer' diesel engine to boost fuel economy on its Legacy, Forester and Outback ranges. The Legacy Saloon is the greenest option of the bunch, clocking in at 50.4 miles per gallon and relatively low emissions - for it class - of 148g/km CO2.

Top Gear's James May reportedly eked out 63mpg while driving the Sports Tour 2.0D version (pictured) of the Legacy for a televised European road trip. The car also has the advantage of a 700 mile range thanks to a large fuel tank.

"With UK diesel market share now running at 40 per cent, this is the answer to many loyal and potential customers’ future motoring needs", says Lawrence Good, MD at Subaru UK.

Prices for the Legacy start at £19,995.