Martin, over two seasons of cruising (we're retired,) we averaged 0.4/gal per hr. Sorry I don't have a breakdown by RPM range. I try to keep RPMs around 25-2800 while underway and never idle for any extended period. Warren & Pattie Updike C320, #62, 1994, "Warr De Mar" Frog Mortar Creek, Middle River Chesapeake Bay