BMW 520d by Nic Cackett

What is it?

We've already been impressed by the 3.0-litre versions of the new BMW 5 Series in petrol and diesel format, but today it's the turn of the certain best seller, the 520d.

The success of any medium sized executive saloon range hinges on the strength of its 4-cylinder diesel model, and the previous generation 520d accounted for the majority of BMW 5-series sales in the UK.

With stakes so high BMW has left nothing to chance - the new 2.0-litre engine is an improvement across the board from its predecessor, certainly on paper anyway.Power is slightly up, from 174bhp to 181bhp, while torque climbs from 258lb ft to 280. As a result there is a mild bump in performance - the 0-60mph time drops by 0.2secs - and marginally better economy at 57mpg compared to 55mpg.

Most significant though is the car's green credentials. Thanks to the introduction of stop/start and a host of other Efficient Dynamics features, BMW has ensured the 520d will be the first saloon in its class to slip below 130g/km.

This means the car will escape the first year 'showroom tax' when it goes on sale, and cost just £90 a year to keep on the road, not to mention drop of two tax bands over the old model for company car tax.