RE: Which fuel???
I'll take 17% oil and a slightly rich fuel/air mixture to 20% oil fuel that's needled too lean any day.
If your engine leans out and loses power in mid flight, close the throttle and land! If you don't throttle down, you're going to dead stick anyway. If you do throttle down, the engine will often keep running instead of dying and you will be able to come around and land.