What Car? Green awards 2008 - Executive cars
Has BMW discovered a secret formula? How else can we explain its total dominance in this category? Well, there's no secret - just top-notch engineering and a determined effort to make its cars as environmentally friendly as possible.
The outcome is that the 318d is the winner here by a mile. Most impressive is its CO2 output - just 123g/km. In this class, its nearest rival (apart from BMW's own 318i) is Audi's A4 2.0 TDI, which emits 144g/km. The 318d also manages a staggering average of 60.1mpg.
BMW's 2.0-litre diesel engine in the 318d has always been one of the most efficient around, but it's now cleaner and more frugal than ever.
It includes the full range of measures in BMW's Efficient Dynamics programme. Aerodynamic tweaks, electric power steering, a change-up indicator and a system to feed power back to the car under braking play their part. All four-cylinder 3 Series also have a system that automatically stops the engine when stationary to save fuel.
BMW has also boosted the 318d's power. It now has a healthy and flexible 141bhp.
The car is smooth and quiet, too. Road and suspension noise are barely noticeable, and you only hear the wind because there's so little else to disturb you. Pin-sharp steering, crisp handling and outstanding grip give a real connection between the car and the road.
Inside, the entry-level 318d is as solid and classy as any other model in the range, and you won't be complaining once you get settled at the wheel. The driving position is just about perfect.
There's plenty of adjustment should you need it, though, while the dash is simplicity itself. There's lots of space up front, while those behind have decent legroom.
Air-conditioning, alloy wheels, an MP3-input socket, six airbags and stability control come as standard, which isn't bad for just over £24,000. Also, although the 3 Series sells in large numbers, it's as desirable as ever, so resale values are strong.
Faults? The 318d doesn't have very many; rear headroom is a little tight, the boot is an odd shape and the looks aren't to everyone's taste.
At 0.201g/km, NOx emissions are on the high side, too, but it's hard to think of a car at this price - or any other for that matter - that succeeds on so many levels.
Buying used There are lots of used 318d ESs about, but finding one with the all-important Efficient Dynamics system is the challenge. You'll pay from around £22,000 for 08-plate cars with delivery mileage from dealers, but prices quickly rise depending on options.
Best buy up to £25,000
BMW 318d ES
Target Price £22,405
Average economy 60.1mpg
Green verdict The 318d indulges you in luxury motoring - without the environmental guilt
Best buy £25,000-30,000
BMW 520d SE auto
Target Price £26,782
Average economy 50.4mpg
Green verdict Even as an auto, the 520d is more energy-efficient than all its rivals
Best buy £30,000+
BMW 530d SE auto
Target Price £34,043
Average economy 42.8mpg
Green verdict Corporate bigwig or eco-warrior? In the 530d, you can be both
With thanks to the Eden Project: www.edenproject.com