BMW’s revised 1 series on sale from the spring finally includes three-door models built at its Leipzig plant and adds new technology delivering, among other benefits, the most economical car the automaker has built.

Technologies such as brake energy regeneration, automatic start-stop function and electric power steering are combined with lower rolling resistant tyres and a gearshift change indicator to encourage economical driving.

These supplement variable valve technologies and high-precision direct injection engines on some versions that boost power output but cut fuel consumption and emissions.

The 118d, now BMW’s most economical car, manages its maximum 60.1mpg fuel consumption in conjunction with more lightweight engineering – it gains an aluminium crankcase to save weight.

Excluding the still-developing hydrogen 7 series model, the 118d also emits the lowest amount of CO2 of any BMW, recording 123g/km (putting it into the UK’s Band C category for vehicle road tax, on which company car tax is also calculated).

Other engines in the revised range post claimed economy improvements of up to 24% compared to the previous model, while emissions have also been cut by up to 21%.

Brake energy regeneration makes its debut on the 1 series and uses an intelligent alternator control and an absorbent glass mat battery to recycle previously lost energy. This technology, also a feature of the latest 5-series, reduces drag on the engine by only engaging the alternator when required to charge the battery and also harnesses overrun energy previously wasted. Bundled under the ‘iGR’ tag, these items improve fuel consumption by a claimed 3%.

Automatic start-stop, standard on all manual transmission models except the 130i, switches the engine off when the vehicle is stationary and gears in neutral. It restarts when the clutch is depressed again and the system can be manually switched off.

The switch to electric power steering results in a 90% energy saving compared to a conventional mechanical hydraulic steering system, BMW said. Other fuel saving enhancements include the air-conditioning power supply being disconnected when not in use and flaps behind the kidney grille  that close for improved aerodynamic efficiency should the engine require less air flow. The feature is also said to improve cold starting times.

Minor interior and exterior styling changes include a larger ‘kidney’ grille for improved airflow, restyled front spoiler, and darker headlamp cover at the front, and restyled rear bumper with new light cluster.

The new three-door version has coupe-like frameless side windows and buyers will be able to choose – at no cost – four- or five-seat layout. The four-seat cabin separates rear passengers by a central storage compartment and they sit in more sculptured seats. Higher quality materials are now used and there are minor changes to the cabin layout.

As an option, Apple iPod or USB stick connectivity is now available, with steering wheel button or iDrive control, and the adaptive headlights that turn into corners with the car have been improved and gain two additional cornering lights.

Despite a lukewarm response from some critics (a cramped rear cabin and harsh ride were early niggles), the 1 series has proved popular with 51,492 sold to date in the UK and over 200,000 worldwide.

The updated line gets its first public showing at Geneva in March.