One thing missing from Brian's equation, is the oil that gets on top of the piston, past the oil ring, and is burned. Blow-by is only a measure of what the cylinder loss is in one direction. Also, with blow-by, there is some oil lost to vapor, that must be condensed out of the hot air, before it can be measured. The " smoke from under the hood" would qualify as oil smoke. A decent "test" nonetheless.