D or I Position
WARNING: This page is about a different car, the 2007 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
In the D position the optimum gear is automatically selected from the 1st, 2nd, 3rd, 4th, and 5th gears, and in the I position the optimum gear is automatically selected from the 1st, 2nd and 3rd gears according to conditions such as the balance between the throttle opening and vehicle speed.