The Good: Some of the 2009 BMW X5 xDrive35d's cabin tech features work very well, such as the iPod and Bluetooth phone integration. Handling at speed is particularly good, and the diesel engine gives it about 5 miles per gallon better fuel economy than the gas version. The Bad: The diesel engine makes for lagging acceleration from stopped, and produces more rattle than we would like. The old iDrive interface is still present in the X5. The Bottom Line: The presence of the old iDrive interface makes it hard to recommend this generation of the BMW X5 xDrive35d, and the diesel engine makes it more suitable for open-road conditions than congested city traffic. Photo gallery:2009 BMW X5 xDrive35dWith a twin-turbo diesel engine, the 2009 BMW X5 xDrive35d lacks the immediate acceleration of the V-8 gasoline version we tested previously, but BMW handling characteristics are there in full force, and the improved fuel economy is a bonus. This full-size SUV features all-wheel drive, and the diesel engine gives it the torque to handle some heavy-duty work. Where the gas version drove like a sports car, the diesel drives and sounds like a fast tractor. One big disappointment in the cabin was the old version of iDrive. The week before reviewing the X5 xDrive35d, we spent some time with the 335d, the diesel version of the 3-series. That car had BMW's radical reworking of iDrive, which proved an excellent interface, and made going back to the old version painful. On the road Although we hate the old iDrive interface, its cabin applications are generally good, so when we took the X5 xDrive35d out for test driving, an iPhone was tethered to the iPod connector and simultaneously paired to the Bluetooth phone system. The phone system in particular works well, making all contacts from the phone available on the car's LCD. Live traffic is a very useful feature on the navigation system, but iDrive makes finding this map difficult.Creeping through city streets, the X5 xDrive35d 's engine sounded like farm machinery, and acceleration was hardly quick, showing noticeable lag before it got up and went. The steering also felt a little loose, something surprising in a BMW. But the tall front seats proved very comfortable, wrapping us in adjustable bolsters. Once we found the map in the horrible iDrive menu, it showed traffic on all the freeways around, helping us find clear roads. And it was on those clear roads that the X5 xDrive35d finally started acting like a BMW. Our car was equipped with Automatic Damping Control, a feature that brings in a sport button for the suspension. On the freeway, with the engine running past its lag point, it was easy to get some real acceleration. And that acceleration didn't want to quit, either, pulling strongly well towards the triple digits. And the X5 xDrive35d got even better after an exit out onto twisty mountain roads. Popping the weird-looking shifter into Sport mode-- a complement to the suspension's Sport mode--the tachometer showed higher engine speeds, giving more immediate power to rush the turns. Once on the open road, the X5 handles very well.Even with the transmission's Sport mode, we couldn't let the speed drop too much before a turn, or the car would be stuck in lagsville. But going in with some speed meant the X5 xDrive35d showed its true colors, staying flat as the g-forces attempted to pull it over. Under these circumstances, it cornered like a champ, making us think it would be best to tackle the densest city streets as if we were on a racetrack. In the cabin There are things we like about the 2009 BMW X5 xDrive35d's cabin tech, such as the wide screen set into the dashboard, with its assistance screen off to the side. You can, for example, set it to show trip information in one side and a map on the other. Other uniquely BMW features are the star and diamond buttons on the steering wheel, which can be set to a number of different functions, such as showing the phone book or changing audio sources. We enjoyed the panoramic sunroof on the X5, an uncharacteristically free feature. As mentioned above, the Bluetooth phone integration is excellent. It makes dialing numbers from your phone's contact list very easy. For security, it also lets you set your own PIN. The navigation system--DVD-based with this older generation of iDrive--does an excellent job of integrating live traffic and alerting you to problems on your route. But it is rather slow, especially when calculating new routes. The new system, which we saw in the 335d, is hard drive based, with more detailed maps and quicker operation. And in the X5 xDrive35d, the old version of iDrive takes you to address entry when you choose the menu item for navigation. To see a map, you have to do four more motions with the iDrive controller. We would prefer a quicker way to bring the map up on the screen. Our test vehicle was equipped with iPod integration and a USB port for thumb drives, satellite radio, and a six-disc changer that read MP3 CDs. The iPod and USB port, situated in the center console, was particularly convenient. We were pleased with the sound quality from the stock audio system in the X5 xDrive35d. It accentuated small door speakers and front tweeters with a center speaker and subwoofer. Clarity was particularly good, as we could hear distinct snaps and clacks in some tracks with complex percussion. Separation wasn't all that great, however, as tones seemed to muddle together, making it difficult to distinguish between singer and instruments. The autohold button behind the shifter provides hill hold capabilities, and lets you take your foot off the brake at any stop.One interestingly useful feature we found was automatic hold. When stopping the car, a temporary parking brake engages, letting you take your foot off the brake even with the transmission in drive. As soon as you give it some throttle, the parking brake disengages. This feature works great for hills and long stop lights, but would be a problem in stop-and-go traffic. Fortunately, you can easily disable it. Under the hood The 2009 BMW X5 xDrive35d gets the same engine as the BMW 335d, a 3-liter, straight, six-cylinder diesel with two turbochargers. The engine uses one small turbo for slower engine speeds, such as accelerating from a stop, and a bigger turbo that takes over when the engine is up to speed. This system is intended to reduce turbo lag, and it largely does the trick. The X5 xDrive35d doesn't exactly bolt off the line, but the acceleration is fairly linear. Although not a hardcore off-roader, the X5 shows long suspension travel when needed.As with the 335d, the engine puts out 265 horsepower and 425 pound-feet of torque, that last number giving the X5 a powerful push when it gets going. Because it's a diesel, engine speeds are low, with redline at only 5,000rpm. But where the 335d would cruise along at 1,500rpm on the freeway, the bigger X5 takes a little more oomph, requiring about 2,000rpm. The weight of the X5 xDrive35d shows in its mileage, getting 19 mpg city and 26 mpg highway in EPA tests. We saw an average of 23.5 mpg in freeway and sport driving. But that still beats the gasoline-powered X5 substantially. We saw about 16 mpg with the 4.8-liter V-8, and the 3-liter, inline, six-cylinder version has an average EPA rating of 18 mpg. Full-time all-wheel drive gives the X5 the capability to handle slippery stuff, but it also comes into play during fast cornering. If you can actually get the power up in a turn, the wheels do a good job of digging in, which keeps slip to a minimum while the sport suspension counters sway. In fact, the X5 only comes second to the Porsche Cayenne GTS in on-road handling for SUVs we've tested. In sum The 2009 BMW X5 xDrive35d comes in with a base price of $51,200, but being a BMW, the options add up pretty quickly. Our vehicle was equipped with the Cold Weather package, for $1,250; the Premium package, which brings in autodimming mirrors, a telematics service, and an automatic tailgate, for $3,200; and the Sport package, with electronic suspension control, for $3,700. Add to that optional Comfort seats for $1,200, a smart key for $1,000, iPod integration for $400, navigation for $1,900, and satellite radio for $595, and the total comes out to--with a $825 destination charge--$65,270. In rating the BMW X5 xDrive35d, we didn't find the diesel engine gave it the same kind of performance advantage as it did the BMW 335d over its gas counterpart. There is a fuel economy improvement over the gas version, but the acceleration suffers--although the handling is still good. The basic functions of the cabin tech, navigation, iPod integration, and Bluetooth phone support are all very good. For design, the old iDrive interface makes it suffer a lot. Now that we've seen the new interface, BMW can't upgrade fast enough.