Originally Posted By: Rolla07
I was rather impressed with the gas mileage of a Silverado I rented last year with the 5.3L. It wasnt as fast as I thought it would be, but the gas mileage was quite impressive. I suppose as long as you have no issues associated to having AFM, its worth leaving it as is.
It varies tremendously across the trucks. I have no experience with AFM in GM cars. In our light duty trucks the programming is very annoying on earlier models. Transmission still shifts too soon and you are into AFM too early IMO. In our 3500 monster vans the shifts are delayed and the AFM stays out of sight, almost hard to notice.
Programming is the key to smooth cylinder deactivation for fuel economy. You can imagine the throttle programming required to change from 6 liters to 3 in a V8! A few mfgrs have it better than others. My Wife's RAM 5.7 is perfectly transparent, if it wasn't for the green indicator light you'd hardly be able to tell.
Like many modern vehicle features this is a shot at trying for the best CAFE numbers. Thank the people at the EPA.