In my experience this business of 'thirsty engines' comes from a) problems with tuning (needles, prop, fuel, exhaust & plug); and b) underpowering the model--too small engine displacement for too heavy or too draggy a model. If an aerobat or anything other than a racer is powered to cruise straight & level at a satisfying speed at half throttle, fuel consumption will be reasonable. If the model is underpowered to the extent that it spends a lot of time flying at wide open throttle, then fuel consumption will be high. Of course some maintenenance is necessary as well--the occasional bearing change, ring replacement, etc.