Classic/Antique Car Repair: 235 timing advance/octane/gas mileage, optimum fuel economy, spectre performance

Question
Hi Brad. I was hoping you may be able to offer me some advice. I have completed a full body-off restoration of my grandfather's 1951 Chevrolet 3100 Pickup. I am a college student and live about 4 miles from home, where my fiancee lives. Consequently, saving money at the pump is imperative to see my baby. But i want to do so without damaging baby #2 (my 3100). I have been playing with the timing advance trying to get optimum gas mileage without hurting the pistons and over heating the exhaust valves. My engine is a 235 I6 from a 1955 model. My timing is currently advanced 15 degrees from TDC and I get about 19 MPG highway. Would it be more beneficial to my wallet to advance the timing even further and switch to a higher octane, stay where it's at, or retard the timing? I would greatly appreciate any knowledge you might be able to share with me about this and any other gas saving tips. I have already switched to a higher ratio ring gear and pinion as well as add a Spectre Performance air intake system. Hope you can find the time to reply. Thanks a bunch!

Answer
If you are getting 19 miles per gallon on that truck, I would saw that you are about max'd out. I don't think that advancing the timing more and running a higher (more expensive) octane fuel will be cost effective. The optimum fuel economy and power will be achieved when all the fuel in cylinder is burned by the time that the engine gets to 23 degrees after top dead center on the power stroke. Most of the time this translates to a spark advance of 40 degrees BTDC at about 2200 RPM. Soooo with 15 degrees advance that leaves 30 degrees to be made up by the centrifugal and vacuum advances.
Brad