'15 Silverado - M and Tow/Haul Modes NOT locking out AFM

[mjj]

I want to turn my AFM back on and see what my gas mileage looks like for a month, but it's getting cold our and soon we'll have winter gas so that will throw my #'s off

That's exactly what I've done over the past month is turn my AFM back on and I've only seen about a 0.5mpg increase. I have a trip coming up in two weeks it's gonna go back off for that so I can again see the difference. But from everyone I've read that has it disabled you don't lose much. To me this makes it worth it to avoid any unknown engine/oil consumption issues down the road and always having that v8 power. Not that I've had an issue with that, the v4 to v8 switching back and forth had been very smooth for me with no complaints on how it actually works.

[tnchevy]

I will be interested in what you find out. I have had my truck for just over a year with a spread sheet showing each fill up and mpg. I plan on taking off my air dam sometime in the next few days and drive for a year without it and compare. By that time I will have talked myself into a new set of LT AT tires so hopefully I will have another year of mpg's to compare with. I would like to disable AFM mainly because I want a good sounding exhaust system and it is just .5 mpg or so then I may just do it. I also don't have a problem with AFM because mine is pretty smooth when going in and out of 4cyl mode. My truck is actually in 4cyl mode about as much as it is in 8cyl (8cyl going up the hills and 4cyl coming back down).