2012 GMC Sierra 1500 Tire Pressure Question

Hummmmmmmmm....what does the door sticker state for unloaded and loaded?

That's what I'd recommend.

The MAX on tire sidewall is the MAX PSI for MAX LOAD on tire.....not normal usage.

When hauling mulch/gravel then air up rear tires so that they aren't overloaded (under inflation kills a tire FAST)
Otherwise run the recommended psi front/rear

X2, max them out for towing.

Former GMC 1500 owner and current F-150 owner. I always run recommended for daily driving (because the engineers obviously recommend it). When towing, I air up to max pressure (less squishy of a ride, less side-side).