In most lube, fuel and air filter applications, cellulose media is a better choice than synthetic media. Again, the reason largely relates to capacity, or filter life. To explain why, a description of the filtering process is necessary.
Cellulose automtoive filter media is manufactured with fibers of various sizes. On the top layer of the media, the fibers are fluffed up, rather than compacted down.
When fluid and contaminants are passed through the media, many particles collect on the fluffy fibers on the surface and don’t travel farther into the sheet. This is referred to as “adsorption” because the particles adhere to the fibers.
The more of this separation technique that a media applies, the more small particles can be separated before they reach the small pore spaces on the screen side of the media. This keeps these small particles from plugging the media.
Another advantage of cellulose filter media is that the media will typically be thicker. The thicker it is, the more time the particles spend traveling through the media. Each time the fluid changes direction around a fiber, the particles momentum keeps them traveling in the same direction they were going and they are driven into the fibers.
This particle separation is referred to as “impingement.” As with adsorption, the more impingement that a media applies, the more particles are separated without plugging the tight pore space on the screen side.
Synthetic media does separate some particles with adsorption and impingement, but the smooth fibers can’t hold the particles in place and they are washed off with the fluid traveling through the media. Synthetic media primarily uses the particle separation technique call “direct interception.” This is how most people think all filtering is done.
Direct interception is simply separating particles by passing the fluid through pore spaces that are small enough to catch them. However, once all pores are plugged with the contaminant, the filter is plugged and its life is over.
Because cellulose media is better at adsorption and impingement, it can remove more contaminants than glass media without plugging pore spaces.
Can a synthetic media be created with the benefits of cellulose media? This remains to be seen. The fact is that cellulose-based media and glass media both have a place in today’s filter market.