I have oil/hot water heat one zone per floor, basement first second floor. Should I set the water temp. To high or low? if I set it high the boiler runs longer but the radiators get hotter and stay hotter. If I set it low it runs for a shooter time but comes on more frequently. What is the most efficient way to set the water temp? I run my wood insert most of the time but I want to get the most out of my oil heat!