TWO of the most popular models from Mercedes-Benz have just got leaner and greener - with CO2 emissions down to just 92g/km.

Called ECO SE, these new versions of the  A 180 CDI and B 180 CDI will be available from January.

Both feature weight-saving measures, powertrain refinements, improved fuel consumption with no impact on performance, and improved aerodynamics.

The changes include the use of an aerodynamic grille element, coupled with underbody panelling and lowered suspension.

And the manual transmissions on each car have longer ratios in the higher gears, an improved energy recuperation system and make use of a lightweight fuel tank to save on weight.

Replacing the current A 180 CDI SE and B 180 CDI SE manual variants, CO2 emissions on the A-Class ECO SE have been reduced by six per cent to 92 g/km, with combined fuel consumption increased to 78.5mpg, compared with 74.3mpg on the outgoing model.

The B 180 CDI ECO SE model's emissions are also down, to 98g/km - representing a nine per cent cut, while the combined fuel figure is improved by eight per cent to 74.3mpg.

Despite the focus on economy, for both models the power, torque, top speed and 0-60 mph acceleration, remains unchanged.

Both vehicles are free from road tax and the Benefit In Kind company car tax band for the A-Class is just 13 per cent, with qualification for 100 per cent capital allowance until 2015.

In addition to the new ECO SE models, the advanced four-wheel drive system first seen on the CLA 250 4MATIC, comes also comes to the A and B-Class from January.

The A 250 4MATIC is available in both AMG Sport and Engineered by AMG trim, with the B 220 4MATIC exclusively in Sport trim. 

Prices are from £21,965 for the A 180 CDI ECO SE and £22,950 for the B-Class variant.