I guess it depends on how you fly it, but I usually climb at 12gph and cruise at 8gph.
At 75% power and at the optimum BSFC an O360 will burn about 9.0 - 9.1 USGPH.
At 65% power and at the optimum BSFC an O360 will burn about 7.8 - 7.9 USGPH.
At takeoff full rated power, (sea level ISA) they should use about 17.5 GPH. This reduces in the climb as mass airflow reduces.
Hope that is helpful.
Not sure what I'm doing wrong (or right), but I typically see 6.5-7.5 gph leaned out in my 9 at ~8000-12000 feet. Climb, I don't recall but probably ~12-14 gph. Mine is injected, standard mags.
Greg
Greg, at those altitudes you are probably right, but there is no way you can develop 75% or even 65% power when LOP. You are in the 50-60% range.