The low-hanging fruit, as the Brits say, has already been harvested when it comes to the reciprocating-piston
engine that burns fossil fuel.

Any technology that the world's best engineering minds have been beating on for more than a century isn't about to
unveil some magic secret that will allow massive gains in efficiency.

Instead, those self-same minds are working at the margins of the coal face (pardon the carbon-laced mixed metaphor)
eking out incremental gains with increasingly ingenious trickery.

The gains are still coming, though.

Even a company with engines as sophisticated as BMW has managed to improve the fuel efficiency of its cars by about
30 per cent over the past two decades.

This, despite advances in performance, comfort, safety and features – all of which mean more weight.

An annual two-day innovation seminar at the company's headquarters here shows the beat goes on, with several fuel-saving
techniques being lumped under the rubric "Efficient Dynamics."

This year, BMW also added a two-day test drive of its latest diesel engines in nearby Salzburg, Austria and a visit to its
cold-weather test facility near the Arctic Circle in Sweden to evaluate the firm's newest twist on four-wheel drive.
 
NEW DIESELS

Carbon dioxide emissions are top-of-mind these days in Europe, where people believe that climate change is not
only human-influenced, but also human-fixable.

With pollution per se – carbon monoxide, hydrocarbons, oxides of nitrogen – having been virtually eliminated from car
exhaust, the next step is to reduce the amount of fossil fuel being burned. That's the only route to lower CO2.

Never mind that the automobile contributes less than a third of the atmosphere's CO2.

The car industry has always been the environmentalists' whipping boy, even if it has cleaned up its act better than
any other industry.

Which is where the diesel engines come in. Practically overnight, we could have about a 20 per cent reduction in CO2
emissions if we switched to diesel.

Traditionally, diesels have been slow, noisy and smoky.

No more.

The 3.0-litre twin-turbodiesel, fitted in various BMWs in non-North American markets, can:

    * spin its rear wheels luridly away from rest on dry pavement;
    * do an 80-to-120 km/h passing sprint in an astonishingly quick 4 seconds;
    * record fuel consumption of around 9 L/100 km in a 220 km/h blast I recently undertook on an autobahn.

Truly stunning.

Only at idle with the window down, say at a drive-through, will you have any aural hint that this is an oil-burner.

We will be getting this engine in an as-yet-undisclosed model or models in the 2008 model year. Not soon enough.

I also drove the BMW marque's smallest car, the 1 Series, fitted with a 2.0-litre four-cylinder diesel.

Essentially two-thirds of the diesel six, this engine is currently offered in two states of tune: 143 hp and 221 lb.-ft.
of torque as low as 1750 r.p.m. in the 118d, and 177 and 258 respectively in the 120d.

Both also produce fewer than 130 grams of CO2 per kilometre.

That's well below the 140 benchmark target set by European Union regulations.

My 120d tester was quick, quiet and very efficient.

The four-cylinder diesel will also soon gain the twin-turbo set-up borrowed from its six-cylinder big brother:
a smaller, faster turbo to eliminate lag; a larger one to provide the necessary volume of air.

The two work singly or together, depending on conditions.

The amazing result: 204 hp and 295 lb.-ft. of torque. Those are almost V8-like numbers, with four-cylinder economy.

The 1 Series (designated a 130d) should be a rocket ship. The twin turbos will also find their way into other larger
BMW models.
 
AUTOMATIC STOP/START

A big portion of the urban fuel efficiency gains of gasoline-electric hybrids stems from the fact that their gasoline
engines shut off at idle.

An automatic stop/start function can do much the same for a diesel or a gas motor not part of a hybrid package,
and with a vastly smaller investment in hardware.

This concept is hardly new. But improved electronic control systems have made it much less intrusive and more transparent.

The 120d I drove around suburban Munich was thus equipped, and it proved to be fairly easy to get used to.

As you glide to a stop, you slip the shift lever into neutral, and the engine cuts out. A quick touch of the clutch pedal or a
wiggle of the lever and it fires up.

This technology, being introduced by some European makers over the next months, is currently only available on
manual transmission cars, limiting its applicability in North America.
 
BRAKE ENERGY REGENERATION

This feature essentially shuts the alternator off under acceleration.

The name sounds like the spin doctors weaseled their way into the engineering office.

I mean, every alternator effectively converts mechanical energy into electrical energy for storage in the battery.

What BMW has done here is shut the alternator off unless the car is braking or coasting.

Thus, all available engine power can be used to accelerate the car more quickly.

Alternatively, it can speed up at the same rate, but use less fuel.
 

ACTIVE AERODYNAMICS

Air flowing through convoluted ducts to cool brakes or radiators uses energy.

Motor-controlled flaps mean these airflows are employed only when needed, improving overall efficiency.