Only 10% of the oil gets filtered? How does it manage to do that? Is there a separate reservoir for that 10%?
If there are 4 quarts in the crankcase and one in the filter, 20% of the oil is in the filter at any one time.
If you are looking for an excuse to run without a filter you need a different one than "a Chevy 235 filter only filters about 10% of the oil".
Cletis, what Hotroddickie said is actually correct.
With a full flow filter everything that comes out of the oil pump goes through the filter before going to the bearings.
A bypass filter actually steals a little oil from the oil gallery before it gets to the bearings and after filtering, returns it to the sump. Therefor the flow through the filter is restricted by a very small return hole or fitting orifice. Out of every quart that the oil pump pumps, 90% of it misses the filter.
The theory is that the at some time between oil changes every cubic inch of oil would randomly pass through the filter.
In real life, because bypass filters were used in the days of non-detergent oils, more of the heavy debris settled to the bottom of the pan then ended up in the filter.
