Back in the late 50's through the 60's the OEM "standard" seemed to be around 3000rpm at 70mph highway speed, but that was also when a 50,000 mile car was considered to be high mileage, and anything pushing 100,000 miles was reaching the end of it's life expectancy, right? I'd much rather be cruising in the 2000 to 2500rpm range myself. Much less wear & tear on the engine, and closer to the efficiency point on most.