M or D ?

[andyjenkins]

Hi guys,
I've got a W204 C250CDI and trying to understand the difference between D and M on the auto box.

From what I can see, if when in D, I can control the gears either using the paddles, or the stick (moving it left / right). And I can do the same when in M. If I go to stall the engine, the car will natually drop a gear (so we're not really in manual are we!).

I'm not sure I've really understood the benefits of D over M, or M over D even. Can someone offer a laymans description ?

 

[st13phil]

With the selector in "D", if you use the paddles or selector lever to change down the result is that you restrict the shift range of the gearbox to whatever number is shown in the instrument cluster, e.g. "4" means that the box will automatically upshift and downshift through gears 1-2-3-4, but will never engage 5th (top gear on your 'box); "3" means that the box will automatically upshift and downshift through gears 1-2-3, but will never engage 4th or 5th.

With the selector in "M" the 'box will remain in whatever gear is shown in the instrument cluster and will not automatically upshift (ever) or downshift unless you go so slowly that the engine would otherwise stall, in which case it will downshift to protect the engine and transmission.