Quoting Removed, click Modern View to seeI guess that maybe that sounded a bit 'smart-A', but that wasn't the intent. Intent was that I believe that we have sort of lost the fox with all the percentages. As has been pointed out early on in thread, ALL of the oil gets filtered......the percentage of total flow going through the filter simply equates to 'how long' a time period will be necessary for all the 6 quarts to be filtered. As to what that exact percentage is, I can't tell yo, because I don't know the clearances, oil pump condition, etc. in any given engine. TOH spread sheet analysis begins will a set of reasonable clearances and your ratio analysis holds water. too. Since I have measured the filter flow volume per unit time on one 8N, IF, I knew the pump volume per unit time on that same tractor at same RPM, then I would know that percentage number........but you see the 'IF'. Based on all the factual info that I have seen, I would feel safe with numbers in the maybe 5 to 20 percent range, which means that in order to get ALL the oil filtered, then we need to operate for a longer period of time if 5% than if 20%. Or stated another way, the more worn out you engine is, the longer you need to operate it to get all the oil filtered. Nothing here of great importance as I see it, since without an engine oil system re-design to make it a full flow system, such as later NAA, hundred series, etc., then there is not really much anyone can do to improve the system.....as I see it. Full flow is only way to ensure that all oil supplied to bearings is passed through the filter immediately before reaching bearings. Contrast that with a no filter system, where all oil supplied to bearings is pulled from the sump, unfiltered. Or with the bypass system where all oil supplied to bearings is pulled from the sump, where over time, little by little, the sump volume has been filtered, but at any given instant, there is unfiltered oil returning to the sump & being supplied to the bearings......sometime in the future, it too will get a chance to be filtered. :) Feel free to disagree......its only an opinion.