I have a 14 Sierra 1500 5.3. Bought it new and it currently has 171,000 miles. I disabled the AFM around 90,000 miles. Haven't had any issues before or after disabling it. Burns about the same amount oil (about a quart between 7500 mile oil changes). Used a Diablo tuner to turn it off. Found it annoying and really doesn't gain you noticeable fuel economy. I check in on a GM truck message board and haven't really seen any issues with disabling AFM.