BMW 118d: One clean, green driving machine

Specifications

Model: BMW 118d 3-door
Price: from £18,225
Engine: 1,995cc, four cylinders, 16 valves, turbodiesel, 143bhp at 4,000rpm, 258lb ft at 2,000rpm
Transmission: six-speed gearbox, rear-wheel drive
Performance: 130mph, 0-62 in 8.9sec, 60.1mpg official average CO2: 123g/km

By the end of the decade, new cars must produce, on average, no more than 130g/km of CO2. Currently most cars emit rather more than this, to the joy of plant life across the world, and some will still do so even after the EU-mandated target is met (assuming it is).

But how will this average be assessed? As an average across a car range based on engine types, or taking every version separately, including LXs and Executives? (Imagine the legions of 1.0-litre special editions.) Or will the average be calculated across an entire corporation, so a Ferrari's excess is offset by a Fiat's frugality? Averaged out according to the previous year's actual sales, with penalties for overstepping the mark? I've asked many engineers at several major carmakers, and no-one knows. The 130g/km average is well-meaning rhetoric, but no one in the EU carbonocracy has actually set out the definition. Meanwhile, with the target date fast approaching, the carmakers are left in the dark.

Luckily, some manufacturers are going ahead anyway and creating some very low-CO2-producing cars. (I hesitate to say "low-CO2 emitting", because emissions suggest pollution and CO2, unlike nitrogen oxides, particulates and unburnt hydrocarbons, is not a pollutant.) One impressive new example is the BMW 118d, now with an "EfficientDynamics" – what happened to inter-word spaces? – package the better to eke out every litre of diesel oil.

The numerical credentials of this engine would have been close to science fiction only a few years ago. Ignore the 118d designation: like the more powerful 120d engine, this is a 2.0-litre unit but here producing 143bhp (21bhp up from the previous 118d) instead of 177. This is backed up by 221lb ft of torque to give the effortless pulling ability typical of the best modern diesels, propelling the 118d from a standstill to that arbitrary 62mph figure in 8.9 seconds.

All well and good; the point is that it does all this with an officially-measured average CO2 output of just 123g/km, the lowest of any BMW-badged car. If a car can deliver all this dynamism and slip comfortably under the CO2 quota, then the future is rosy.

To go with the newly efficient engine range is a new body style . It's the three-door that we all expected at the breed's launch in 2004, and it transforms the 1-series from slightly awkward frump to desirable compact. In a way it takes over from the old 3-series Compact, a truncated-tail three-door not reprised in the current 3-series range.

The three-door's sill-line is straight, so it no longer looks as if it has melted in the middle, and it gains both frameless doors and a "faster" tailgate angle. All facelifted 1-series, regardless of door count, get neater, more assertive bumpers and lower valances, while the front grilles, which BMW still describes as kidney-shaped even though no living creature's renal equipment is remotely similar, are now bigger so more air can sate the turbodiesel intercooler's airflow appetite.

So what is this EfficientDynamics all about? All new 1-series cars, apart from the 116i and 130i (the two extremes of the petrol-fuelled range), have a stop-start system, the sort of thing you might remember from aeons ago with the Fiat Regata ES and later the VW Golf Ecomatic. The idea is the same – with the car stopped and the gearbox in neutral the engine stops until you depress the clutch upon which it restarts automatically – but in this modern, high-tech BMW it works rather more smoothly, discreetly and reliably.

Another key feature is the Intelligent Alternator Control (IAC). Whenever the engine is turning but not under load, which means when decelerating or braking, the alternator (or generator, in everyday terms) engages to charge up the high-capacity battery. Otherwise the alternator is disengaged unless the battery is getting too low on charge. In other cars the engine turns the alternator all the time, even when the battery is charged. Turning an alternator uses energy, and the IAC system can reduce fuel consumption by up to three per cent.

But it's yet cleverer than that. An alternator that's charging hard is a big drag on the engine. So if the alternator is engaged when you're slowing down or braking, and has some hard charging to do in order to recover the energy taken from the battery when driving under power, then that "drag" helps with the braking. That means you don't have to brake so hard, and as braking involves the dissipation of kinetic energy as heat, less energy is wasted. It's called regenerative braking, as used by hybrids. So, when slowing down at least, the 1-series behaves a bit like a hybrid.

Two more items in the EfficientDynamics armoury are electric power steering, widely used in rivals and some other BMWs (new Mini included) and a gearshift indicator to suggest when an upshift might be good for fuel economy. Some Volkswagen Golfs had this back in the 1980s but, again, today's version is more sophisticated.

So, feeling smugly green, I set off in the 118d. Immediately it feels unique among today's compact hatchbacks for blending that compactness with the very BMW sensation of rear-wheel drive. The demeanour feels taut and pure, and the new electric power steering is good enough not to have the stodgy, artificial feel too often found in such systems. Electric power steering feels more natural when the motor is in the rack (the part that moves from side to side to turn the wheels) rather than in the column, and that of the 1-series is so designed.

On sensible 16in wheels the 118d rides with suppleness over Britain's broken roads, and the whole thing is a dynamic delight. Even the engine? Yes – its power delivery is typical modern diesel, relaxed but insistent, a touch gruff aurally but never instrusive. There's a sweetly-shifting six-speed gearbox, and the more you drive the 118d the more you wonder why you should ever need any more car than this.

Interior furnishings fitted and finished every bit as well as those of bigger BMWs add to the feeling of completeness. It even seems to have more rear-seat space than I remember from earlier 1-series encounters, posssibly because expectations of roominess are lower in a three-door car. Clearly the mind is playing tricks here, but the 118d is nevertheless a proper five-seater.

Best of all, though, it's a lively car which can cover about 60 miles on a gallon of fuel according to the official figures. We like that, and the £50-a-year road tax, very much indeed.

The rivals

Audi A3 2.0 TDI, from £18,315

BMW-matching quality, lively pace, good looks, but neither as rapid nor as frugal as the BMW.

Volvo C30 2.0D, from £17,795

Glassy tailgate, individual rear seats, lots of style, good to drive, but again lacks BMW's pace and frugality.

Volkswagen Golf 2.0 TDI, from £17,320

Shares underpinnings with the Audi including 140bhp engine, is better value. A good choice.

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