What exactly is "S" mode in transmission?
 

hey guys...might seem like a bad question; but...
what exactly does it do when i put it in "S" mode?
when is it right to use this mode?
how is it diff from "D"?

Thanks!

S in Sport Mode. The transmission will start in a lower gear from a standing start and will hold on to the gear longer before shifting up. As well it will downshift when you apply the brake....oh yeah you will use more gas too!

No wonder I use more gas when I drive in "S" mode.....:D

The transmissioin does NOT start out in a "lower gear"; the transmission always starts out in 1st gear in Drive or Sport mode (it WILL start out in 1st, 2nd or 3rd gear in Manual mode). Sport mode holds the transmission in 1st, 2nd, etc. longer than Drive mode will (it will take it to max red line with full throttle), AND when suddenly releasing the throttle, as you would do moving through the "twisties", it holds the transmission in what ever gear you are in when you released the throttle to allow for engine braking and faster recovery without down shifting as you get back on the throttle. It also more agressively (readily) un-locks the torque converter and/or kicks down the transmission for additional power accelerating out of the "twisties". And yes, it does use more fuel.

I've never been able to start from a dead stop on 3rd gear in M mode. It automatically goes down to 2nd gear. I have a 2005 X3.

might be cuz its an X3. But my X5, can start off in 3rd in manual mode, sloooww, but can do it.

It's much more fun to drive it in "S" mode. You will get about a 10-15% reduction in gas mileage, but it's worth it.

honestly with gas prices today nothing justifies a 10-15% reduction however to each his own

My guessed is that only the 4.4i, 4.6is, and 4.8is can start from 3rd. My 3.0i X5 also will only start in 2nd from a dead stop in Manual mode.

So Its like a semiauto?