What to worry, I cruise at highway rpm also around that and safely arive also.. hahahah.. but i notice that the best speed to maintain at highway for my car is around 120kmh, above that its eating too much fuel already..
some people think that having the rpm at lower speed, u will end up saving fuel, its not always the case though.. minor ratio increase might be ok but if alot of increase, then it will be too heavy thus needing more power to maintain the speed = more fuel.. if not mistaken the final drive alone is about 300 - 400.. check with spare part shop ler..