Driving diesel: BMW 123d

CNET Car Tech tests the 2007 BMW 123d, a diesel car unavailable in the U.S.

Wayne Cunningham Managing Editor / Roadshow
Wayne Cunningham reviews cars and writes about automotive technology for CNET's Roadshow. Prior to the automotive beat, he covered spyware, Web building technologies, and computer hardware. He began covering technology and the Web in 1994 as an editor of The Net magazine.
Wayne Cunningham
4 min read

BMW 123d
The BMW 123d isn't sold in the U.S., and that's a shame for a variety of reasons. James Martin/CNET

With falling gas prices dampening enthusiasm for alternative fuels, and poor economic conditions causing automakers to tighten their belts, plans for new diesel car launches in the U.S. have slowed. However, diesel engine cars still present a good option over gasoline-powered cars, generally getting much better fuel economy. Although automakers scaled back their plans, Bosch, which makes diesel engine components, still wants to change the perception of diesel cars in the U.S. so the public will be more receptive, and even demanding of this technology from automakers.

To that end, Bosch loaned us a 2007 BMW 123d, a car you can't currently get in the U.S., so we could see how it performed in comparison with gasoline cars. Combating the image of soot-spewing diesel trucks, Bosch adopted the slogan "good, clean fun" for its diesel technology, and the BMW 123d was a means to make sure we had some fun.

BMW started selling its 1-series car in the U.S. last year, as the 128 and 135, in coupe and convertible formats. While we found both cars to be very enjoyable, the 123d is a hatchback, a style that makes much more sense with the diminutive sports car. Increased rear headroom makes the cars rear seats more usable, although still tight, and the hatchback means you have substantially more cargo area. After driving the 123d, we really wish BMW would bring the 1-series hatchback to the U.S., with a diesel or gas engine. It didn't hurt that this 123d was also fitted with an M kit, meaning a sport-tuned suspension.

M shifter
This 123d was fitted with an M package. James Martin/CNET

It's obvious the 123d is a diesel from the outside, mainly because of the racket from its turbocharged 2-liter four cylinder engine, fed by a common rail injection system. The exhaust also smells a little different from a gasoline car, but the emissions are clear, with no obvious soot or particulate matter. This 123d doesn't have the urea emissions clean-up system used in other diesel cars being sold in the U.S., and doesn't meet the Euro 5 emissions standards, which goes into effect in September.

From inside the car, the engine sound isn't an issue, as BMW does a good job with its noise and vibration insulation. But a glance at the tachometer, with its 5,000rpm redline, gives you a clue that this isn't the kind of high-stepping engine we're used to seeing. Putting the six-speed-manual transmission into gear, the 123d pulls smoothly, without the kind of juddering we might expect, considering that engine noise. In fact, it feels just like a BMW.

Besides its high-mileage engine, this BMW 123d has another fuel saving trick up its fender. When we pull to a stop at a red light, the engine shuts off. Although a common experience in hybrids, in a diesel it's a surprise. But as soon as we push in the clutch, when the light turns green, the engine cranks back to life, and everything's back to normal. Running accessories and air conditioning defeats this system, as the car needs power when stopped. That idle stop-start technology, which saves fuel in heavy traffic or at long lights, has caught on in Europe, and should make its way stateside soon.

BMW 123d instrument cluster
With its redline at 5,000rpm, we're due for a lot of shifting. James Martin/CNET

A spec sheet for the BMW 123d shows a peak torque figure of 295 pound-feet from 2,000rpm to 2,250rpm, a lot for such a small car. As a point of comparison, the BMW 120i, with its 2-liter four-cylinder-gasoline engine, only outputs 154 pound-feet of torque. Given the specs, we can't wait to try a fast start. But the 123d requires a different approach than a gasoline-engine car. We only let the engine speed rev a little more than 2,000rpm before dropping the clutch, and are treated to shrieking rear tires as the little hatchback takes off. But there is no rest for the wicked, as the quickly rising tach needle means another shift, then another, and another, and, yet another.

As a few false starts showed, it's easy to redline the 123d. Running it in second gear, as we might do with a car with a gasoline engine, and the tach needle hits 5,000rpm, causing an enforced engine slow-down. Given that the engine doesn't complain when pushed near redline, it's easy to go over. During our week with the car, we get used to a lot of shifting work when we want to get moving fast. And this little BMW feels very fast, even though, according to BMW, it only gets 6.9 seconds to 62 mph. Of course, the short gearing contributes to the need for all this shifting, and isn't all that economical. At Interstate speeds in sixth gear, the engine is running at about 2,500rpm, far from its more frugal 1,500rpm cruising speed.

Putting the 123d through some mountain road paces, pushing its limits in the corners, the M suspension shows pure BMW handling. The steering keeps the front pointed true, while the back end slides out just enough to be useful--it's what we love about BMWs. However, the diesel engine adds a new twist. Normally, we would use third gear, or even second, for this type of cornering. But in the 123d, the third gear brings the revs up toward the redline, so we got used to making our approach in fourth gear, and finding that we still get plenty of power pushing the accelerator at the apex. Along with its powerful torque, the engine puts out 201 horsepower at 4,400rpm.

Now the really good news: Its fuel economy as measured in the European Driving Cycle is 36 mpg city, 53 mpg highway, and 45 mpg combined. We weren't gentle with the BMW 123d, and averaged a few economy of about 43 mpg. However, that's still a great number for fuel economy, and means a long time between fill ups for the 13 gallon tank. The 123d also proved as much fun as the BMW 335d, a car that can be bought in the U.S. and averaged 30.9 mpg in our review.