I believe the best mileage my friend's 1968 Z28 ever achieved was when he went skiing in Mammoth Lakes, CA and got 18 mpg, with 4.10 gears and F60-15 Goodyear tires. Years later, we drove up to Mammoth in my 1998 Z28 with a 6-speed and got 30 mpg. In daily driving on the street in the Los Angeles area, the 1998 Z28 would only get about 13 mpg as sitting in traffic takes its toll on mileage.