BMW heralds its X5 sport utility vehicle as a "Sport Activity Vehicle." The tactic is designed to focus attention on the vehicle's on-road handling and driving dynamics, but it's also an attempt to eliminate any need for the automaker to apologize for the X5's limited cargo space and restricted off-road capabilities. Regardless, consumers don't seem to mind, as they've been snatching up the SAV since its introduction in 1999.
BMW delivers the goods with three capable gasoline-fed engines, including a new 555-hp twin-turbocharged X5M, that keeps the ute's fun-to-drive factor higher than nearly every SUV on the road. So with on-road performance such a high priority, why has BMW decided to fit the 335d's 3.0-liter turbodiesel into its biggest SUV? More to the point, how does the fuel-efficient oil-burner fit into the mix and does it affect drivability and performance in the process? All that and more after the jump.
Photos by Michael Harley / Copyright ©2009 Weblogs, Inc.
Just over ten years ago, BMW debuted its first sport utility vehicle. Its introduction helped mark the start of the unibody crossover era which is still dominating the market today (the Mercedes-Benz ML320 did beat the X5 to the showroom by a year, but it rode on a body-on-frame platform). Unlike the Lexus RX300 (also new for 1999), which shared components with the sedate Toyota Camry, the E53-platform X5 was a close cousin to the E39 5 Series – an award-winning sport sedan.
Manufactured in Spartanburg, South Carolina, the first-generation X5 was offered in many different configurations with both six- and eight-cylinder gasoline powerplants and a multitude of trim level, including the "X5 Security," with bullet-resistant windows and ballistics-resistant armor for high-risk clientele.
The second-generation, E70 debuted as a 2007 model. Wider and longer than its predecessor, the updated X5 was now available with an optional third-row, bringing seating capacity up to seven. Loaded with new technology and innovations, including composite front quarter panels and an extensive use of aluminum components, the X5's curb weight was down and overall balance nearly perfect as on-road performance was still a primary engineering objective.
Today, BMW offers the X5 with a choice of powerplants. The standard engine is a 3.0-liter gasoline inline-six (260 hp) or an optional 4.8-liter gasoline V8 (350 hp). Those seeking even more performance (and a quenched ego) will seek the X5 M with its twin-turbocharged 4.4-liter V8 (555 hp) and laundry list of go-fast components. While the new X5 M scoots exceptionally well around a race circuit, its existence isn't nearly as significant as the new xDrive35d -- the efficient diesel variant.
With the exception of a small badge on the lower part of each front door and slight trim changes to the front grille, the diesel model is nearly indistinguishable from its gas-fueled 3.0-liter (xDrive30i) sibling. However, lift the hood and an all-aluminum, twin-turbocharged, 3.0-liter oil-burning inline-six greets you, with common-rail direct fuel injection (feeding fuel at up to 26,000 psi) and a compression ratio of 16.5:1. While the 265 horsepower at 4,200 rpm isn't particularly impressive at first blush, like all modern diesels, it's the torque output that's important. At just 1,750 rpm, the high-compression oil-burner churns out 425 pound-feet of twist (trumping both diesel offerings from Mercedes-Benz and Volkswagen) sending its prodigious grunt through a ZF-sourced six-speed automatic (6HP26 TU) gearbox.
All standard X5 models, including this diesel model, are fitted with BMW's xDrive all-wheel drive system. Under normal conditions torque is split favors a rear bias (40/60). The torque split, through its multi-disc clutch, is variable; ratios constantly change based on road conditions. The vehicle's stability control electronics (DSC) take advantage of its adaptive ability to enhance handling. If DSC senses oversteer, it's able to send the maximum amount of maximum to the front wheels. If the electronics detect understeer, the front wheels receive no torque. As expected, xDrive works completely seamlessly and automatically.
Our diesel-powered xDrive35d ("35d") test vehicle carried a base price of $51,200 (the gasoline-fed xDrive30i starts at $47,500). This particular Mineral Green Metallic over Tobacco Nevada leather model was fitted with the Premium Package, Cold Weather Package, Technology Package, heads-up Display, satellite radio and Comfort Access, among other features. It also had the Sport Package, which includes 19-inch wheels and electronic damping control, bumping the MSRP to $66,620. (BMW has been carrying a $4,500 rebate/incentive on its diesel models for several months, effectively lowering the base price below the gasoline model.)
Our week with the 35d was busy. We ran errands, drove soccer carpools and visited business clients. We climbed over mountain passes, sped down the highways and sat cursing in traffic. One morning we loaded the whole family for a one-day round-trip from Los Angeles to Morro Bay (California's central coast) and the 425-mile trip was easily covered in a single tank of fuel.
From the driver's seat, the view outside is commanding. Thanks to its unibody construction, and a seat raised off the floor, there's a nice footwell with generous legroom and a large dead pedal for resting the left leg. The sport seats (standard in the Sport Package) are well-bolstered and offer medical-grade lumbar support. Our tester wasn't equipped with the optional third-row seating (skip it unless you need it for small kids), but the second row is roomy and incredibly comfortable for any sized adult thanks to artfully sculpted driver and front passenger seatbacks. Both the console-mounted transmission shifter and parking/emergency brake are electric, thus freeing up a large bit of storage in the center console (plus there is a big glove box on the passenger's dash). Overall cabin ergonomics are typical BMW -- once you're introduced to the layout, and become familiar with switchgear locations, it soon becomes second-nature.
Outward visibility is good for an SUV. The exterior mirrors are large and well-positioned for viewing the flanks while parking near curbs or driving through traffic. The Technology Package on our 35d included the "Rear-view camera." Although these back-up video devices are a godsend on just about every SUV, we found this one on our X5 quite useless. We would be several seconds into our reversing maneuver when the camera would finally initialize -- too late for whatever hapless animal or vehicle happened to be sitting immediately behind us. The "Park Distance Control" parking sensors with the visual display and audio tone, on the other hand, were priceless.
Like most BMW models, the steering effort on the X5 xDrive35d is high but very accurate (while the X5 30i and 48i are offered with BMW's controversial Active Steering option, the 35d is not). At speed, the heavy steering lends a substantial and very stable feel to the overall driving dynamics. There's no wandering or tracking -- traits commonly associated with traditional trucks and SUVs. Most BMWs feel securely "planted" on the highway, even with irregular road surfaces, and the X5 is no exception.
With handling dynamics taking precedence on the engineering check list, the effort has paid off. Even in diesel guise, the BMW X5 is one of the few SUVs that's truly enjoyable to flog in the canyons. In addition to the lightweight, multi-link rear suspension, the front setup of the X5 is unique in that it's a double wishbone multi-link design with upper A-arms combined with double-pivot lower links similar to the setup on the 7 Series (at its introduction, it was the first non-strut design on a BMW since 1961 -- with the exception of the mid-engine M1).
Like the Porsche Cayenne and Infiniti FX, the two other top sport-oriented contenders in this segment, the X5 more than holds its own far above posted speed limits. Body roll is well controlled (especially with our test model's Electronic Damping Control) and grip is excellent thanks to 255/55R18 tires on all four corners and plenty of negative rear camber. Brake late, get on the throttle and all 425 lb-ft of torque pulls the 'ute through the bend with ease. The X5 is one of those rare SUVs that can shame many self-proclaimed sport sedans on a circular onramp, but if pushed too hard, the X5 will safely understeer and remind the driver that they're getting too frisky with nearly 5,300 pounds of machinery. In all honesty, you really aren't supposed to have this much fun in a diesel-powered truck.
We don't normally electronically test for acceleration numbers, but this time we made an exception. We happened to have a 2008 X5 3.0si model within arm's reach for a few timed comparison runs (they both share 3.0-liter inline-six powerplants) and using a rather simple Escort G-Timer GT2, we left the transmission in "Drive" and ran each SAV on a long straight for a quarter mile. Without any of the diesel's slight turbo lag, the gasoline model was marginally quicker to 20 mph. After that, the turbocharged diesel took the lead and never looked back. The gasoline variant hit 60 mph in 8.42 seconds while the diesel model did it in 7.28 seconds. The quarter mile came up in 16.37 seconds at 84.70 mph in the gasoline model, while the stump-pulling diesel ran the same distance in 15.58 seconds at 90.60 mph. The diesel doesn't just pull better numbers -- it feels remarkably faster than its gasoline sibling.
The particular sound of the X5 35d deserves mention. While the inline-six is noticeably smoother than Mercedes-Benz, Porsche, and Volkswagen's six-pot diesel offerings, it's also louder. The diesel mill's unique clamor permeates through the firewall like a trustworthy Cummins at low speeds. However, at highway speeds it's unnoticeable. It's not annoying (in fact, one passenger thought it sounded "cool"), just very different from BMW's familiar silky inline-six gasoline note.
While the torque and power of the engine is exceptional, the fuel economy is downright extraordinary. The EPA rates the X5 xDrive35d at 19 mpg city and 26 mpg highway (for comparison, the gasoline-fed xDrive30i is rated 15 city and 21 highway). During our highway trip up the California Coast we were sipping diesel at a rate of 29.4 mpg, according to the on-board computer, and burning less than a quarter tank of fuel every 125 miles. After one full tank of city driving, we hand-calculated 19.31 mpg overall (for comparison, the same driving in the 3.0-liter gasoline model averages 14.48 mpg). Our math says that the X5 diesel will earn about 25 percent better real-world city fuel economy, and about 30 percent better on the highway, when compared to its 3.0-liter gasoline sibling.
A few more honorable mentions... Bonus points go to the X5's excellent adaptive xenon headlamps. Not only do they track corners and illuminate far down the road, but the fog lamps are programmed to automatically (and individually) provide fill light during low speed maneuvers. The seats (front and rear) feel firm at first, but your spine will be very happy after a seven-hour shift in the cabin. The optional heads-up display didn't make our greatest hits list, as we couldn't see it with polarized glasses during the day and its limited information was rather useless at night (M cars get a unique HUD with a more useful information).
The arrival of the diesel to the X5 lineup really shouldn't disturb owners of either V8 model. Those horsepower connoisseurs enjoy the instant power underfoot and rarely check the monthly fuel bill. However, owners of the 3.0-liter petrol-six shouldn't test drive the diesel model -- it will make sleep impossible knowing a more powerful, quicker, and much more efficient model is on the showroom floor for the same dollar.
Without question, we really enjoyed the BMW X5 xDrive35d. While it is not the fastest, most cavernous, or best handling sport utility on the market, the innovative diesel variant offers more than a generous balance of those three important traits -- and it delivers very impressive fuel economy -- without sacrificing anything to its gasoline equivalent.
Photos by Michael Harley / Copyright ©2009 Weblogs, Inc.