I've regularly been getting 13-14 mpg in a stock 1950 3100 with an un-rebuilt 216. Tires are about 30" diameter. Driving is a mix of 30-40 mph roads and 50-55mph freeway driving.

1950 Chevrolet 3100 (Ol' Roy)

1939 Packard Standard Eight Coupe (The Phantom) | 1956 Cadillac Coupe de Ville (The Bismarck) | 1964 Ford Galaxie 500 coupe |1966 Ford Mustang (Little Red) | 1969 Pontiac GTO (The Dishpit) I 1979 Ford F-100 | 1976 Ford F-150 (Big Red) | 1995 Ford F-150 (Newt)