Some years back I had the opportunity to drive my at the time tired 235 a 12 hour 600 mile none stop trip at 3000 rpm due to malfunction of my over drive gears caused by yours truly . That rpm gave me 60 mph. and it climbed hills better and got better gpm s then when the over drive worked and I ran at 2,200 rpm.
I just completed a 1,700 mile round trip turning between 2,500 rpm and 3,000 for 14 hours at a time traveling 65 to 70 mph and when I let the rpm drop to low below 2,500 it struggled to climb hills .
All that being said ,when traveling less demanding country roads at a leisurely pace less rpm s work fine .
Hope this helps .
John
