im running some of my engine 20+ min on 8oz of fuel and still landing w/ a third of a tank. most of the time at half throttle or above.
your way too rich, lean your engine till it peaks out (till you cant hear the rpm's increase anymore then back it out 1/3 ish of a turn, that should be plenty rich)
your idle is harder to adjust, sit around at the field and watch people fly their planes. ask someone for help that never seems to have problems with his engines, get his advice on how to set the idle and highspeed correctly


ive flown for 47min and 15 sec on 8oz of fuel before (wildcat 10%). with a gms.47 for the engine and the gp rapture as the plane. your nextar should be able to get 30+ min w/ a properly tuned engine and throttle control.