For those folks who prefer the convenience of a spin-on filter, I've been doing a little research on the online WIX filter specification pages. Most spin-on engine oil filters have a micron rating of anywhere from 25 to 32- - - - -pretty coarse media. Since a bypass-type filter doesn't have to flow enough oil to keep bearings lubricated and/or hydraulic valve lifters pumped up, one of those filters can have a much denser filter media. I've found some spin-on filters intended for industrial hydraulic fluid applications with media rated for 3-5 microns. That's roughly equivalent to straining out BB's instead of golf balls! Just because a filter doesn't happen to have an advertised use for motor oil doesn't necessarily mean it can't be used that way. A 3 micron filter won't clean things up as well as a Frantz, but it will certainly outperform any motor oil filter, cartridge or spin-on. Just be sure to put a 1/16 inch diameter restrictor orfice somewhere in the plumbing for the spin-on adapter that will keep most of the oil headed for the engine bearings instead of back to the oil pan.
Jerry
