How effective is the stock...

[Chuck Leeper]

Unlikely. As long as it's clean and not leaking, the efficiency is still going to be 58%. The only things that would reduce that would be obstructions, dirt, or damage.

Not so.. As the solder joints on the tube to fin connections deteriorate, due to [insert my original comment], the efficiency will go down...

 

[Chuck Leeper]

Whatever............