Others have followed, but the BMW X5 invented a class. As BMW's 3 Series defines the sport sedan, the X5 defines an expanding group of big, powerful SUVs that shine for their on-pavement agility and lightning acceleration, with an emphasis on luxury appointments. Climb out of a truck-based luxury SUV like the Cadillac Escalade, and the X5 feels as capable on the road as the big BMW 7 Series sedan (even though it isn't). Improvements for 2004 are more extensive than any since the X5 was introduced five years ago. And a new high-performance 4.8is model has been added to the lineup. Logic? You'll have to set it aside to appreciate the BMW X5. The X5 is 2.5 tons of speed, comfort and prestige. It's quicker away from traffic lights than most cars, and capable of nearly 150 mph, though we certainly don't recommend driving a vehicle this tall that fast. Its steering is precise and it's exceptionally stable at supra-legal speeds. Massive tires contribute to impressive cornering grip and stopping power. The X5 offers nearly all the bells, whistles and high-tech gizmos that you'll find on the most expensive sedans in the world. A big V8 delivers the ultimate X5 thrill, but it's also available with an outstanding six-cylinder. That trademark BMW twin-kidney grille indicates its owner is successful. It also indicates BMW's reputation for quality and driving excitement. Moreover, the X5 delivers most of the attributes that made SUVs popular in the first place. It works well in foul weather and easily negotiates muddy trails. It offers the commanding seating position many drivers prefer. It looks tough and polished at the same time. Now let's get back to logic. BMW says the X5 is designed for all roads, meaning superhighways, graded gravel or logging trails. It's not intended for carving your own road, or fording shallow streams or climbing boulders. In fact, the X5 is not capable off road, not when measured against sport-utilities that are capable. The X5 offers less cargo capacity than nearly any other SUV of its size and weight, less even than a BMW 5 Series wagon, and its high floor makes loading cargo more challenging. Though it handles well for an SUV, its weight and height simply won't allow it the quick transient response of a sport sedan or sport wagon in the same price range. Compared to other BMWs, the X5 is not the ultimate driving machine, and its fuel mileage is poor in comparison. It also costs more than some comparably equipped, very good luxury SUVs. For 2004, the X5's look has been freshened, with a redesigned front end, new taillights and new wheel designs. Mechanically, both manual and automatic transmissions have been upgraded to six-speeds, with a more powerful V8 and a new, more sophisticated all-wheel-drive system called xDrive. There's more standard equipment, including rain-sensing wipers and a power passenger seat in all models, and new options like heated rear seats on the six-cylinder X5. New for 2004 is BMW Assist, a telematic system with automatic accident notification and other premium services. Forget rational vs. emotional. If you seek a luxurious sport-utility that makes a fine, highly useful everyday vehicle, with high style and modicum of off-pavement capability, the 2004 BMW X5 is the benchmark.