Back when I was selling an upsized Frantz-type filter for 18-wheelers, they claimed it would filter down to the 2/10 micron particle size. The element they were merchandising fit the Luberfiner 750 housing, and we just changed the filter, never the main sump oil, and added enough oil to account for what was lost while changing the filter element. That was usually about 1.5 gallons on a 15-gallon system.
We would do an oil analysis at every filter change, which was usually at 10,000 or 15,000 mile intervals. At 100,000 miles, the oil was still testing within normal limits for severe service. I was impressed!
Jerry
