Texas highways are 70-75mph so usually i find myself doing 80-85mph when the traffic at 5-6am just won't let me drive slow without a bunch of angry drivers lining up and flicking me off as they pass me by.

It runs about 4k-4,200 rpm at these speeds. Is gas mileage the only thing that suffers at this speed? Or will prolonged driving at 80+mph cause the engine to lock up? (I had a motorcycle motor lock up on me driving highway speeds but it was a high mileage used 250cc that had been sitting for awhile so not the best condition)

It really doesn't feel like the engine is struggling at this speed but i'm wary about keeping her there for too long. It doesn't get near the redline and i'm definitely not hitting 90+.