After ten years with my motor and 50 thousand miles I wonder why so many fret over RPMs. I am not specifically referring to the OP. It's epidemic. It can't be fuel savings I hope. Are we afraid they are going to wear out? Most motors seem to have a subjective sweet spot and, for my ears (which are rather poor), it is usually not down in the middle teens. Venturi effects,
oil splash, and many other things seem to argue for some standard other than slower is better. Once more I am not finding fault with the OP---I just don't understand this anxiety about RPMs.