I overinflated the tires on my vette to 45 PSI because it stiffens the sidewall and makes it turn quicker. I’m still getting about 9 MPG. On 92 octane premium.
Of course, hussein could suggest that eberyone install a set of donks. 22” tires are sure to increase your milage.
Among other things, that's why manufacturers have a specific number. A specific value also helps to keep SUVs from rolling over too easily (though oddly enough Corvettes are quite high on the actual use, rollover frequency list too.).
Be careful out there. ;-)
Well, if you put large diameter tires on the rear and small diameter tires on the front, you'll be going downhill all the time which should provide a big improvement in fuel economy.