Though launched with new engines only last November, BMW's Mini hatchback will get new lower-emissions motors from August production.

The introduction of such technology as brake regeneration and auto start-stop reflect changes being made to BMW brand models as well.

Efficiency improvements range from a 7.2% to 11.9% reduction in CO2 emissions and combined EU cycle fuel economy gains of between 6.5% and 12.8% - the recently introduced diesel model with its new 1.6-litre PSA engine (replacing a 1.4-litre Toyota unit) shows the biggest gains.

Brake energy regeneration, auto start-stop function and switch point display are all being added in a package at no extra cost.

Brake energy regeneration works by using an intelligent alternator control (IAC) and an absorbent glass mat battery to recycle previously lost energy, which saves fuel. The IAC reduces drag on the engine by only engaging when required to charge the battery, whereas a traditional alternator is always taking power from the engine.

Additionally, the energy generated by the engine on over-run (under braking or descending a hill) was previously wasted. Now this lost energy is utilised by the IAC to charge the battery.

The auto start-stop function, available with manual transmission cars, automatically switches the engine off when the vehicle is stationary and the driver puts the car into neutral. To restart the driver only need engage the clutch again before pulling away in the normal manner. The system may be de-activated when not required.

Just-auto sampled this system on a manual BMW 320 coupe-cabriolet earlier this week and found it worked very well, instantly re-starting the engine almost imperceptibly.

Switch point display aids drivers of manual transmission Minis in selecting the most economical gear in which to drive. The engine management system analyses speed, road situation and accelerator pedal position and based on this data calculates optimum gearing. The ideal gear is then displayed by number in the cockpit display.

BMW noted that the switch from the Brazilian-made Chrysler engine in the previous Mini hatchback models (it continues for another year or two in the convertibles which are still previous-generation) to the new line developed in conjunction with PSA had already reduced CO2 output per car by 14%.

"Putting that into perspective, the industry average was recorded at a lowly 0.3%," the automaker said in a statement.