I've owned two owb's now and I seem to burn less wood and form much less tar and creosote by keeping both temps up on the high side. My primary combustion chamber stays cleaner as well as the secondary burn chamber and heat transfer tubes. Mine comes on at 177 and shuts off at 185. The refractory brick seems to maintain enough heat so that when the system calls for heat the smoke lights off within 30 seconds or less. Less smoke equals happier neighbors as well as very little smoke seeping through the cracks of my old two story house. I've played with many different combos over the years and higher is what I've found works best for a gasifier, with a small differential. My current furnace is a puny little Pro Series 100. It's amazing what that little fart can do on such a miserly little amount of wood. Marty