Tony, you're right. Eventually all of the oil will go through. I don't know exactly, but I would estimate about 10% of the oil that is pumped goes through the filter. On a "full flow" system, the filter is in line after the pump, all of the pumped oil goes through before it goes to the engine. With the bypass system, some of the dirt goes through the bearings and valve train. That's why non-detergent oils were used, the dirt settled to the bottom of the pan rather than being suspended in the oil with detergent oils. The big item it to keep your oil changed before it gets dirty.
