For some reason I think that I have read where more synthetic oil will increase engine run time.. Am I headed in the right/wrong direction with this thinking ? I don't want to go so low that I burn/seize an engine up.. Thanks
Reducing the total oil content will increase the run time - it's as simple as it seems, more "go juice" (methanol or whatever) per unit volume by having less non-volatile components (oil). To first approximation, it doesn't make any difference what type of oil it is. A secondary issue is how much drag/friction the oil provides -- the less friction, the less HP removed as friction, so you can use a smaller venturi and get the same power.
How low you can safely go depends on the engine, and how you are running it. This is endlessly hashed over in the past, I am not up for another round, and Randy has a pinned topic at the top of the board that tells you most of what you need to know - *accurately*. At either extreme, running Fox fuel (29% castor) in a modern engine will make it run poorly and require service in short order, and the right fuel for a modern AAC engine will likely destroy a Fox in very short order.
As a general rule, set up the engine to run the best, and put in whatever size tank is required to get through. You *never* want to compromise the engine run to save fuel, only do it in emergencies or special circumstances where you can't do anything else. And then, next time, make it so you don't have these special circumstances (like building in the fuel tank, or making only 1" thick tanks fit, or something like that).
Brett