Saab

Conventional has never been a word you associate with Saab, and it has taken a different route to improving economy and efficiency.

In the Seventies, the brand was a turbocharging pioneer, delivering big engine performance from small, fuel-efficient four-cylinder units.

It’s a policy that’s become fashionable with rival marques in recent years, but Saab still leads the way, as all its powerplants now use forced induction.

However, the firm has steered clear of other fuel-saving technology, such as stop-start and regenerative braking, concentrating instead on Biopower versions of its 9-3 and 9-5.

These use E85 – an alternative fuel made up of 85 per cent ethanol and 15 per cent unleaded. Bosses claim running on E85 reduces CO2 emissions by 70 per cent and boosts power by around one-fifth. Better still, the cars can use standard petrol without modification.

The snag is that the UK has only a handful of E85 pumps, which will make refilling tricky.

A more mainstream alternative is the diesel line-up. The 178bhp twin-turbo in the 9-3 is especially impressive –it returns 53.3mpg and emits only 139g/km.

BEST ECO BUY: 9-3 TTiD saloon