[JethroBodine]

Mcgiiver- The best way to get a definitive answer is to test it yourself. Someone with your exact same car could get a different result due to driving style, fuel pedal control, terrain, wind direction,... whatever. Discussing BSFC charts, aero modifications, weight saving, et al, will only get you started. Get an instant fuel meter of some kind, MPGuino, Ultra Guage,
ScanGuage,... and keep track of your daily numbers. Our member deathtrain fills up weekly at the same pump and logs in his fills in the garage here. Could be a good way to check the results of weekly 52 vs. 55 vs. 57 mph runs.

Have fun and let us know what you find.