Buick 2007 Rainier Owner's Manual page 116

DRIVE (D): This position is for normal driving.
It provides the best fuel economy for your vehicle.
If you need more power for passing, and you are:
•
Going less than about 35 mph (55 km/h), push
the accelerator pedal about halfway down.
•
Going about 35 mph (55 km/h) or more, push
the accelerator all the way down.
You will shift down to the next gear and have
more power.
Downshifting the transmission in slippery road
conditions could result in skidding, see "Skidding"
under Loss of Control on page 298.
DRIVE (D) can be used when towing a trailer,
carrying a heavy load, driving on steep hills, or
for off-road driving. You may want to shift the
transmission to THIRD (3) or, if necessary, a lower
gear selection if the transmission shifts too often.
116
THIRD (3): This position is also used for
normal driving. It reduces vehicle speed more than
DRIVE (D) without using your brakes. You might
choose THIRD (3) instead of DRIVE (D) when
driving on hilly, winding roads, when towing
a trailer, so there is less shifting between gears
and when going down a steep hill.
To shift to the THIRD (3) position, you must
first press the large button on the shift handle.
While the button is pressed, move the shifter in
the THIRD (3) position.
SECOND (2): This position reduces vehicle speed
even more than THIRD (3) without using your
brakes. You can use SECOND (2) on hills. It can
help control your speed as you go down steep
mountain roads, but then you would also want to
use your brakes off and on.