How many times have we had this debate already?
niky said it best: YMMV.
Some claim exceeding sidewall max doesn't result in wearing the centers fast; that could very well be. But I've had it happen so it could very well NOT be too.
I laugh at those who think +4 psi is fraught with risk. Geesh, get a grip.
Burst pressure on tires in good shape is around 200 psi.
Bulges and cord or belt issues can happen regardless of pressure.
The OEMs are in a tight spot with psi recs; if enough customers whine about a slight jiggle in the ride then all sorts of things that require effort and expense happen, so they rec lower pressures than those of us who prioritize low r.r. over no jiggling.
Raising psi vs lowering r.r. is not a linear relationship thus the first smaller increases in psi give the most r.r. and fe results; after that the returns diminish. You will NOT get another 7 or 9% fe with an additional 15 psi on top of the first 15 psi increase.
Regarding psi I paint with a rather broad brush; seems to me in most applications there is a zone between manufacturer rec (often around 32psi) +5psi, and lower than 50 psi, where tire pressure happiness will be found... so basically 37-47psi.
I fine tune that by driving on a dry dusty road then on a paved road then looking at how much of the tread at the shoulders is still dusty; I want it to look even so the lightly loaded rear tires on a fwd car end up about 5 psi lower than the fronts.
Then there is the resolution of the whole psi thing; gauges vary wildly AND pressures do too depending on temps and loads and trip lengths and whatnot so does it make sense to get hung up over one or two or even three psi? Whatever the gauge says, it's probably more important simply to have fairly equal pressures on each tire on each axle, just so each tire is doing it's share.