Both A180 CDI SE and B180 CDI SE manual variants will be replaced by the new ECO SE economy models. The A180 CDI ECO SE offers a claimed average of 78.5mpg and CO2 emissions of 92g/km, compared to 74.3mpg and 98g/km of CO2 for the outgoing model.
The Mercedes B180 CDI ECO SE benefits from similar improvements, offering 74.3mpg and 98g/km of CO2 as opposed to the 68.9mpg and 108g/km of CO2 of the car it replaces.
Consequently both are now free to tax, as opposed to just the A-class, and benefit from low company car tax bands.
The ECO SE models, which will become available in January 2014, feature aerodynamic improvements, weight-saving measures and powertrain tweaks in order to boost their efficiency without compromising performance. Mercedes claims that for both models the power, torque, top speed and acceleration is unchanged.
Other additions to the range include new '4MATIC' all-wheel-drive editions of the A-class and B-class. The system will be offered on A250 models, in AMG Sport and Engineered by AMG trims, and on the B220 exclusively in Sport trim.
The system, which debuted in the Mercedes-Benz CLA, distributes torque between the front and rear axles via an electro-hydraulically controlled multi-disc clutch unit. It operates automatically and, when required, can send as much as 50 per cent of the power to the rear wheels.
Prices for the new Mercedes A180 CDI ECO SE and B180 CDI ECO SE start from £21,965 and £22,950 respectively.
All-wheel-drive versions of the A250 4MATIC cost from £28,985; the B220 4MATIC is priced upwards of £28,135.