I don't think it's cost effective to boil with oil without an RO. AG is right, with raw sap you are looking at $7.50 to make a gallon of syrup.My figures may be a little rough, but, even if you concentrate to 8%, you'll still have $3.00 per gallon in fuel.This is considering that oil is $3.00 a gallon.(for easy figuring)When I concentrate up to 17%-20% I can get that # down to $1.00 +/- a gallon. All the other comments in this thread are correct, everbodys' situation is different. I couldn't have put a wood fired evaporator in my sugarhouse, as the back wall of the building is only 20' to the only general store in town! Flying wood embers would not help the neighbors business much! So much for my speel---OIL IS GOOD FOR ME!!