I have an 06 Sierra Denali and I have been reading up on this "lean cruise" and sounds like the PCM will always command 14.7afr if I am hearing this correct. Does the PCM command 14.7 if in open loop if you set the parameters to see lets say 15.5afr? Does switching to SD change any factors? I'm just trying to get a little better mileage while cruising is all.
Thanks for any input.