I think my cruising rpm is fairly stable. On interstate posted speeds of 70 mph, I typically run 75-80 mph, in 6th gear, rpm's something less than 4K rpm. On primary roads with posted speeds of 55-65 mph, I typically take 5-7 miles above the posted speed, in 6th gear, rpm's 3.5 or less. On facilities such as the Blue Ridge Parkway with a posted speed of 45 mph, probably mostly in 4th and 5th gears, rpm's in 3 to 3.5 range