... filtering efficiency needs a follow-up since I don't know it offhand.
I know on the x4651 (Fram PH2 size) it is 98.8% efficient > 30um and 87.97% efficient > 20um per the Ecogard rep I talked to.
I know someone else had contacted them about a different size filter (don't remember model off hand) and were given slightly different numbers for that specific model.
I do agree for $2 I would use one of these filters for most any "routine" OCI. Problem is nobody around me has them on the shelf, and online they are more than a Fram orange can at Walmart.