JonCraig wrote:My newer Briggs say, "use no oil". I assume that's EPA junk, so I oil them anyway. (Note I'm talking the pre-cleaner; not the paper air filter itself.) I use cheapo 3-in-1 oil, have been for years, and it seems to work fine. It's my understanding that the oil is just there to get the foam "sticky". I would think any viscosity at all would do the job adequately. And my guess is that it takes *far* less oil to do the job than what most people put on. I try to wring mine out really, really well, to the point that it just barely leaves a "film" on my hands, rather than making an oily mess.
My $0.02.
--JC
the ones that say "use no oil" are because the pre-filter is directly up against the paper element and oil from the filter will contaminate the paper element. The ones that you do oil usually have a mesh , or they are in contact with the expanded metal outer casing of the paper element , so there is no direct contact with the oiled foam and the paper element.
yes most any oil will work (We use drippings from drained oil bottles so we get a mix of anything between 80W90 and 5W30 synthetic) but generally supposed to use the same oil you use in the crankcase - your thoughts are correct that the oil is just to moisten the foam (fills the porous gaps of the filter to trap dirt and dust that passes through) and if correctly oiled, won't affect air flow - We've even used bar oil - (high tack, no sling, very sticky) - no problems when correctly oiled .
Failing to oil a filter that is designed to be oiled results in the filter actually passing dirt through to the intake.
How poor are they who have not patience. What wound did ever heal, but by degrees? - Iago (Othello Act II, Scene 3)