I just did a 400k/250mile road trip to San Jose and back. Since I bought the X5 (2002 3.0d, 75,000miles) three weeks ago I'd only been able to drive it around town, so I was looking forward to seeing how it would do on a longer trip.

My route took me along the Pan American highway from 1,500 ft. above sea level up to 12,000 ft. and then back down to about 2,500 ft. during the first 75 miles. Very steep climbs and descents and lots and lots of curves! I came back home down the coastal highway, 60 miles farther but mostly straight and flat.

Going up: There's a slight whistle when I get on the accelerator. Looks from other posts like that may be an intake boot leak... Sounds like a supercharger!
It handled GREAT around the curves and I never felt like I needed more power than what I had in order to pass the busses, tractor trailers or 1970's Datsun pickups with cattle in the back, that I encountered on my way up.

Going down: If what I experienced here is normal, then I may just have to get used to it. Going down hill and breaking, with the car in "D", it would often down shift, (I'm assuming from 4th to 3rd but since the readout only says "D" I'm not positive,) which is fine since the compression helps with breaking, but if I got to a point where I needed a little acceleration it would rev up to 2,800 or 3,000rpm before shifting up. I wound up putting it in "DS" and just shifting manually. Any thoughts on this?

Coming home: AWESOME! Speed limit on the coastal highway is 100kph/62mph. I don't go much over since speeding tickets here can run up to $400! Everything felt good. There's another lower mountain pass for about 25 miles before I get home and besides the whistle, everything was good.

I filled up before I left and reset the kpl/mpg gauge. When I pulled in the garage I had averaged 11.9kpl/28mpg! I can live with that!