But if you drive at steady 70-90mph speeds on the highway it appears that the gas mileage is the same, correct? I can shift between modes and the tach is unchanged...anybody?

Put it in "S" mode and you get 100 hp more just like the button they have for the m5. :rofl: Don't listen to me, I'm just being silly.

"S" or sport is fully auto. "M" or manual mode is semiauto in that you can select each gear manually as long as the computer doesn't think you will over-reved the engine.

"S" mode does nothing when you're at a steady speed. Switching between "D" and "S" simply tell the tranny CPU to use the appropriate seperate "shifting/holding" programs.

I've noticed that "S" mode does actually do something at steady speed (well when you want to pass...). It won't require as much gas pedal to drop a gear for the added power it thinks you are looking for. Does that make sense? I guess it sounds better in my head.

Yes I agree, the shift up is much sooner and with less pedal...in fast and heavy interstate traffic I tend to just stay in S mode.

I notice too that in sport mode the consumption needle goes like in drive if you don't floor with the acceleration. At the same use of drive, normal drive, in sport mode the fuel mileage looks to be the same.
Someone can confirm it?

Chip - it's both. You can leave it in S mode, and it contiues to shift automatically, or you can change gears yourself pushing up or down on the gearstick in a semi auto mode.

Yes, D & S highway fuel mileage will be exactly the same IF you don't play with the throttle.

This is not intended to be a jab... but honestly ladies and gentlemen, you need to read the manual that came with your X. We are driving a pretty complex vehicle and there is a large amount of useful info in the manual that can serve you well while keeping your X running better and longer.

-RSZ