Three hours of cutting is a very long time. If I am cutting very hard or dry wood with full-chisel chain, it can get dull before I finish a full tank of gas (well under an hour).
OK, I didn't know that about the time, so maybe part of my problem is I just have too high of an expectation.
Does your new chain match the markings stamped on your bar (pitch, gauge, number of drive links (DL))?
The new chain specifically stated it fit my saw model. I have a poulan pro 221, maybe 8 or 9 years old.
Does your saw have an adjustable oiler and is it fully opened?
It has an auto-oiler, no way to change the amount. I have cleaned it and the oil opening is clear as far as I can tell.
Does your saw chain throw oil from the bar tip when engine is revved out of wood?
A little, not much. Could this be part of the problem?
What are you cutting (species, dirty wood, dead on the ground, dead standing, dry, etc.)?