down firing a boiler

Jack Demczuk

I have a boiler that I recently down fired to .85 gph. It used to be 1.35 but I no longer use the indirect water heater and converted that to gas so I figured down firing would save me oil by being more efficient. The question I have is, is down firing really going to save me money? It now takes longer for the boiler to get steam out to all the radiators, although they all get hot, and now the burner runs for several minutes whereas before it would run for one and stay off for one. When I do a combustion efficiency test I get an efficiency of almost 85% whereas before it would only be 80% and my stack temperatures are reduced from 550 to 425 degrees. someone once told me that ideally you want your burner to run as long as possible and be on the verge of not getting steam to all your radiators but creating just enough. Is this true? Any help on this topic would be greatly appreciated.
-Jack