The Mercedes A-Class and B-Class are now available in a new ECO SE grade that brings reduced emissions and enhanced fuel economy as a result of weight-saving measures, aerodynamic improvements  and engine refinements.

The new models, available from January 2014, feature a new aerodynamic grille, under-body panelling to smooth airflow and lowered suspension.

The A-Class is lowered by 10mm at the front and 15mm at the rear, while the B-Class drops by 20mm at the front and 15mm at the rear.

The ECO SE models use a manual transmission with longer gear ratios, plus an updated energy recuperation system and a light-weight fuel tank.

The new models replace the existing A180 CDI SE and B180 CDI SE models.

In their place, the A180 CDI ECO SE achieves 78.5mpg compared with the outgoing car’s 74.3mpg, while CO2 emissions drop by 6% to 92 g/km.

The B180 CDI ECO SE sees its emissions cut by 9% to 98 g/km, while economy improves by 8% to 74.3mpg.

Mercedes say power, torque, 0-62mph times and top speeds remain unaffected.

Also available from January 2014 will be a new 4Matic four wheel-drive option for both A- and B-Class, borrowed from the new CLA 250.

The 4Matic system uses an electro-hydraulic clutch to distribute torque between front and rear axles, and the system is capable of sending up to 50% of the engine’s torque to the rear axle as required.

The system is available on the A250 in Sport and Engineered by AMG trim, and the B220 in Sport trim.

The new A180 CDI ECO SE starts at £21,965, with the B180 CDI ECO SE at £22,950.

The A250 4Matic AMG Sport is available from £28,985, with the Engineered by AMG trim at £30,905.  The B220 4Matric Sport starts at £28,135.