best way to explain it i believe is
a V-8 has 8 cylinders, MDS when active runs the engine on 4 cylinders, without harming the engine & it is suppose to save gas
to simplify things
your transmission has 5 gears & 5th overdrive
MDS ONLY kicks in while the transmission is in 5th overdrive & you are on flat ground or going down hill
If you don't want MDS to kick in, just make the single shift down to where you see a 5 light up on your dash readout.
5th overdrive will not display any number on your dash readout
that is an over simplified explanation, but, it is the easiest way to explain it
yes, 1 more to the right & you will see the light with the 5 go out
that is when the computer takes over & allows the vehicle to go into MDS mode, when there is no need for power, such as climbing a hill it will quickly shift into 5th or kick into MDS mode on flatter terrain, most of the time you won't even know that it shifted or changed modes.
Sometimes when climbing a steeper hill, you may notice your speed dropping when you are using cruise control, then the auto pilots speed sensor sends a signal to the computer(s) & tells them that the speed is below what you set it at. At this point if the setting gets say below 7 or 8 miles an hour below your chosen setting, you WILL feel it kicking out of MDS & shifting down & it may surprise you with the power burst