My 1982 Kawasaki 750 Spectre gets in low 50s mpg range. I am not a hard rider and bike is very well maintained. Shaft drive has low overall gearing which negatively impacts mileage. Regular unleaded gas (preferably Chevron for cleaning additives)is fine and higher grades over regular have no benefit whatsoever. Watch yout tire pressures, at least 28 rear and 32 front.