Better full-flow filters have absolute ratings nearing 20 microns, but many engineers still think the 10-15 micron particles do the sneakiest harm in the long run. Oil filter efficiency improves ...

Opening up from, say, a 5-micron secondary filter to a 15-micron filter may mean less frequent filter changes and less loss of performance associated with plugging and low fuel pressure ...

As Penn State architectural engineer William Bahnfleth has shown, while HEPA filters ring the bell at the top of the MERV scale, an idealized MERV-13 filter picks up nearly half of 0.1-micron ...