Incline? Maybe for traveling up hills or it could be a 1st gear you are mistaking the "I" for. Some autos have a 1st ,2nd, and then "D" for Drive. These gears are used for climbing, such as when driving on steep hills or can be used for towing. Most people never use them. I read that some years of the autos actually have an "O" for Overdrive. It may be only on the GXP auto. Not sure. Maybe for the sport package only too.
From the Owners Manual:
Intermediate (I): This position is also used for normal driving. However , it reduces the vehicle's speed without using your brakes, for slight downgrades where the vehicle would otherwise accelerate due to steepness of grade, If constant up shifting or downshifting occurs while driving on steep hills, this position can be used to prevent repetitive types of shifts. You might chose Intermediate (I) instead of Drive(D) when driving on hilly and winding roads.
I know the "I" setting in our Cobalt kicks butt big time:
It increases line pressure in the transmission for harder/snappy shift points. And it engages "engine braking". And with the Cobalt (4 speed auto-4th is overdrive) it will hold 3rd gear instead of shifting into overdrive, the little guy will hit 130 in 3rd. :lol:
Remember reading/getting something from Pontiac a couple years ago for auto transmissions (wife discarded) D for highway (so 5th engages), 4 for in city driving so 5th doesn't. Could I be intermediate 2&3rd, L for just (low) 1st?