The reason my .26 powered plane used so much fuel was I had the guys driving at 65 mph for most of the 50 mile lap, instead of a more logical 40 or so, which the more experienced guys did.
At that speed I expect I'd have used maybe 6 oz.
Used a 9x4 prop.
On a Kadet Senior (which shows up winning at the Ca. Marathon way too often) 65 mph is easy with an OS 70, and little fuel consumption.
The marathon event at Baker runs from a lakebed next to the freeway up about 2000 feet over a mountain which is something over 4000' then down about 1000 feet and return..
Engine power doesn't change much.
I'd made up a position indicator repeater to watch while flying, with throttle position and elevator position calibrated for speed for my next atttempt which hasn't happened yet.