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2017 GMC Sierra 1500 SLE Question


New Member
Apr 10, 2021
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Ontario Canada
Hello, I just bought a 2017 GMC Sierra 1500 SLE.

When I watch the fuel Econ gage I see that it switches from 4 pistons to v8 back and Forth. I see that when going the same speed or taking foot off gas it runs 4 pistons but any kind of acceleration it runs v8. Is it possible to allow more tolerance so it runs in 4 piston mode instead of v8 when doing accelerating less then 2000 rpm? Or ability to toggle between the two modes so I can shutoff v8 when not towing??

It has a 6.2 Engine

Also is a tuner chip worth it to save some fuel economy?

Pretty sure the 4-8 deal is automatic, but maybe a tuner could modify that. In the '12 Charger with the 3.6l it was necessary for acceleration.
If you didn't see it on the gauge, would you care? It's doing what it needs to keep as efficient as possible.

If anything the tuner is usually used to get more power out if the engine, and that means more fuel generally.
The computer handles the 4-8 mode, a tuner can turn it off. That may come with it's own issues though, if the system is off for say 30,000 miles and then turned back on, the lifters may stick. If you shut it off I would say don't ever plan on turning it back on. I don't think a tuner can adjust when it comes on or off
That is called AFM (auto fuel management) and was first introduced in 2007 1/2 in 1500 5.3 engines and 2009 on the 6.2
In the beginning AFM caused some horrendous engine oil consumption issues GM tended to ignore it for a while and then finally addressed the issue sometime around the 2012-2013 models not sure what they did to fix the issue but I wouldn't be afraid of anything 2014 or newer
But the true mileage gain of the AFM system has been debated and many feel it's only worth 1 mpg so it is worth it in the long run?
Lots of engines were replaced on the early models and some people never did get assistance goggle it: "GM AFM oil consumption issues" if you have a few hours to burn....
Many people with the older trucks buy the Ranger plug in tuner to turn off AFM and never look back.....
A tuner can disable the AFM but to do it right the AFM lifters need to be replaced with standard lifters on the AFM cylinders.
They are still having problems with the lifters on the AFM engines to this day. I think they changed the name to Dynamic Fuel Management or the like but it's still wiping out cams. I have seen one that went bad in 5k miles.
I read somewhere they are discontinuing the 5.3 AFM engine.