The results are too wide ranging to cover all models so let's find out what has happened to the 1 Series for the moment. It is now the most fuel-efficient vehicle BMW has ever produced with builtin Brake Energy Regeneration system, automatic stop-start function, electric powersteering, low rollingresistant tyres, crankcase with lightweight aluminium and gearshift-change indicator on the dash to tell the driver when to change gear to get the best from the engine. Add to this variable-valve technology and high-precision direct-injection engines and the result is more power, less fuel consumption and lower emissions.

The BMW 118d is now the company's most economical car and manages 4.7L/100km (57 mpg) and the C02 emission figure is an amazingly low 123g/km, well below the EU target of 130g/km within the next few years. Other engines in the 1 Series range show economy improvements of up to 24% compared to the previous model and emissions have been cut by as much 21% . . . and not at the expense of a lively drive. The 1 Series is powered by a range of engines whose power outputs have increased by up to 20bhp, which actually pushes up onthe-road performance figures.

The Brake Energy Regeneration technology is a first in the 1 Series. The system uses an Intelligent Alternator Control and a special battery to recycle previously lost energy, saving fuel. Also, the energy generated by the engine on over-run, which is normally wasted, is now used by the alternator control to charge the battery. The Brake Energy Regeneration system alone accounts for a 3% improvement in fuel economy.

The stop-start function is standard on all manual transmission models, except the 130i. It switches the engine off automatically when the car is stopped at traffic lights if the car is in neutral. The engine restarts when the driver engages the clutch. The electric powersteering saves 90% of energy compared to the conventional system and the electric motor only works when required, turning corners for example. Even air con is less wasteful as power is disconnected from the drive train when not in use.

The improvements flow to the petrol-powered engines also. In the 118i, a new fourcylinder direct injection unit, the 0-100km dash has marginally improved to 7.7 seconds, power output is 143 bhp (up 14bhp), peak torque is 190Nm (up 10Nm), combined fuel consumption is 5.9L/ 100km (up 24%) and C02 emissions are down by over 20%.