I prefer water for heat , it's more consistent, and you can control it w/ a small ball valve at the intake to help control how much hot water goes into the intake. It will warm up much faster than exhaust gases, if you hook up one side to the thermestat housing , and the other side to the suction side at water pump. It will heat up almost immediately, and run consistantly. Thats my 2 cents , proven on mine to me.
