You are rolling on about $1200 to $1600 worth of rubber, why would you over inflate the tires to squeeze a couple of extra MPG. An under inflated tire will not apply the proper pressure to the center part of the tread and the edges will wear out before the center. An over inflated tire will have so much pressure, that the center will bulge and wear prematurely.
Lets say that the properly inflated tires are good for 50K miles and the over inflated tires only last 25K. To cover the same 50K miles you are going to spend $1200 more, That would buy 300+ gallons of gas or enough to drive 6000+ miles. Now lets throw in a couple of other factors, the ride is terrible and you don't have the proper contract patch so your braking is compromised. Stick with the manufacturers recommend pressure or maybe 2 PSI above.