2009 BMW X5 xDrive35d
2009 BMW X5 xDrive35d. Click image to enlarge

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2009 BMW X5

Kingston, Ontario – If any type of vehicle is well-suited to a diesel engine, it’s a truck. But not just pickups: SUVs too, as many combine the towing and off-road abilities of a true truck with performance, comfort and convenience features usually found in cars.

In recent memory, only a handful of SUVs sold in North America have been available with a diesel engine. And all of them – two Jeeps and three Mercedes-Benz models – have been powered by Mercedes motors. (Expand the scope of discussion to include cars and you can add the VW Jetta and Mercedes E-Class to the list.)

Notice the trend? The engines, if not all of the vehicles themselves, hail from Germany. For 2009, another German automaker joins the diesel fray: BMW adds two diesel models this year, one of them a 3 Series sedan (covered in a separate review) and the one you’re reading about now, the X5 xDrive35d.

Both use the same engine, a 3.0-litre inline six-cylinder engine that employs two turbochargers to boost power output to 265 horsepower and 425 lb-ft of torque. BMW invited journalists to sample both vehicles on a drive that took us from Kingston north to the town of Merrickville and back. After overnighting in Merrickville, we got to start our second day of driving on the kind of cold winter morning typical for eastern Ontario.

2009 BMW X5 xDrive35d
2009 BMW X5 xDrive35d. Click image to enlarge

When cold, there is some diesel clatter, but that disappears once the engine reaches operating temperature. In fact, once warm, it’s nearly impossible to tell this motor is a diesel when it’s running: it is smooth, quiet and pretty well does away with the sooty, smelly exhaust that marked diesels of past decades.

The engine is particularly strong at low speeds (torque peaks at 1,750 rpm) but more surprising is how much power remains available at higher revs; redline is 5,000 rpm. Noise is muted, and the sounds that do make it into the cabin under heavy throttle are more like those of a gasoline V8 than a diesel six.

BMW pegs the X5 diesel’s average fuel consumption at 9.3 L/100 km, and claims a zero-to-100 km acceleration sprint time of 7.4 seconds.

If you discount the engine’s torque-heavy performance, the rest of the driving experience is exactly like that of a gasoline X5. The suspension tuning is similar, producing a comfortable ride with good handling (for a crossover) and BMW’s excellent all-wheel drive system had no problem handling the snowy and icy road conditions that prevailed during our day’s worth of driving.

Like the rest of the X5 line-up, the diesel engine is available only with a six-speed automatic transmission, this one borrowed from the V12-powered 7 Series for its torque-handling capacity. In Europe, the X5 is offered with two diesel engines: the same one we get here, and a less-potent version that’s used in the xDrive30d model. Interestingly, while past X5s have been available even with a manual transmission – even in North America – all X5s sold here and across the pond are automatic only.

2009 BMW X5 xDrive35d
2009 BMW X5 xDrive35d
2009 BMW X5 xDrive35d. Click image to enlarge

The new diesel engine uses a combination of urea injection and a selective catalytic reduction catalyst in the exhaust to keep nitrogen oxides (NOx) emissions to a minimum. The urea injection system uses uncreatively-named “exhaust fluid,” which is stored in a reservoir accessible under the X5’s hood.

Total capacity is 25 litres, stored in primary and larger secondary containers; the primary one is heated, as the exhaust fluid freezes at minus 12 degrees Celsius. BMW says 25 litres of fluid should last the engine’s 20,000-24,000 km oil change interval, and it’s covered under the manufacturer’s warranty as a regular maintenance item.

The U.S. Environmental Protection Agency (EPA) says the engine cannot be run without exhaust fluid. To prevent drivers from using their diesel Bimmers without the fluid, the X5 warns first when there’s enough fluid left for 1,000 miles (1,600 km) of driving, and again when 200 miles (about 320 km) worth. Run it dry, and the car won’t start.

The only difference between the diesel engine in the X5 and the one in the 3 Series is that the X5’s version gets a more sophisticated exhaust gas recirculation (EGR) system that can better handle the higher stresses of towing. The X5’s stability control system also incorporates a trailer towing program designed to eliminate trailer sway at high speeds. The X5’s towing capacity is 6,500 pounds (2948 kg).

The BMW diesel sold here incorporates a few technical differences designed to reduce noise and vibration. Most are upgrades to the engine’s internals – there’s a reinforced crankcase, offset piston wrist pins and swirl valves in the intake air stream – along with an under-vehicle trim piece that reduces engine noise heard from outside the car, and reduces aerodynamic drag, too.

2009 BMW X5 xDrive35d
2009 BMW X5 xDrive35d. Click image to enlarge

There’s also a ceramic heating element built into the climate control system that heats cabin air until the engine is hot, and augments the engine’s heat in light-load situations. Part of a diesel’s efficient operation is due to the fact that less of the fuel’s energy is turned into heat. That means less heat transferred to the coolant, and in turn less warmth that can be pulled into the cabin.

The X5 xDrive35d, which is on sale now, comes with a starting price of $62,200 in Canada. That’s $4,000 more than the base price for the xDrive30i model – not surprising, since BMW is marketing the diesel powerplant as a premium engine choice.

It’s easy to question that choice; there’s an argument to be made that doing so will prevent most drivers from ever experiencing a diesel (and hopefully enjoying said experience) for themselves. I think, however, that if the technology is accepted by buyers of these premium vehicles, diesel power will catch on among the general population, and lower-priced diesels will appear.

That all hinges on the public’s acceptance of diesel engines like BMWs; and if the people don’t like this motor, well, sorry, but they don’t get much better than this one.

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