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Synthetic oil filter versus regular cellulose oil filter

Synthetic oil filter versus regular cellulose oil filter

Carmakers recommend synthetic oil to reduce engine wear and extend the time between oil changes. But the oil filter has to remain effective during those extended oil change intervals. So many oil filter manufacturers have developed hybrid oil filters that combine conventional cellulose filtration materials with synthetic glass and “glass-like” fibers. Some filter manufacturer’s refer to them as synthetic oil filters, but that’s a bit misleading. No motor oil filter manufacturer is making a 100% synthetic oil filter. They’re really made with a mix of organic cellulose fibers and synthetic fibers.

This article explains the difference between a high mileage extended drain interval hybrid filter and a conventional cellulose oil filter that is designed for 3K mile oil changes.

How a conventional oil filter is made

• Cellulose filtration media is made from a combination of organic fibers made from wood pulp, cotton, and other cellulose fibers that are formed into a sheet.
• The sheet is pleated and formed around a center core and the ends are mechanically fastened or glued
• The top and bottom edges of the pleats are glued to a resin impregnated cardboard or inserted into a metal end cap filled with adhesive.

How a hybrid synthetic oil filter is made

Synthetic glass is a general term that can refer to fibers drawn from molten silica (fiberglass) or thin fibers made from any petroleum based plastics like nylon or polypropylene.

The synthetic fibers can be made into fabric sheets using traditional weaving processes. However,  non-woven hot-melt techniques are more cost effective. To make non-woven fabric, a dense mat of fibers are continuously placed on a conveyor and fused together by a hot roller. The density of the fibers determines their filtering abilities.

In most cases, the fabric is then corona treated to give the fabric an electrostatic charge. During the corona treating process, some materials such as fiberglass and nylon give up electrons and become positively charged, while other materials such as Polypropylene, Vinyl (PVC) collect electrons and become negatively charged (more on static charge later).

Once formed into fabric, the material is pleated and fused end-to-end using heat melt methods. The top can bottom edges of the pleats can also be heat melted to end caps or left uncapped.

The pleats are then formed around a supporting metal screen or filter core to maintain stability under pressure.

How conventional oil filters filter oil

The three steps of oil filtration in a cellulose oil filter— adsorption, impingement, and screening (direct interception)

Step One: Adsorption

During the manufacturing process, cellulose fibers are absorption-verus-adsorptionabraded to make them thicker and fluffier which increases the fibers’ surface area. The additional surface area allows the fibers adsorb more of the smaller particles before the oil travels around the fiber.

The higher the surface area, the higher the adsorption rate of the filtration media.

Step two: Impingement

Whatever particles aren’t captured by way of adsorption continue to travel around the thick cellulose fibers until they are driven into the fibers by the force of movement. In other words, the particles are driven into the fiber at a greater depth than the electrostatic attraction that happens at the surface in the adsorption process. This particle separation is called impingement. As with adsorption, the more impingement a media provides, the more particles are separated without plugging the voids between the fibers.

Step three: Screening

As the name implies, screening is the process of capturing particles by trapping them in the voids between the fibers. Adsorption causes the smallest particles to cling to the fibers. Impingement causes the next largest size fibers to be driven into and captured by the fiber itself. Screening the last opportunity to trap the largest particles that have escaped the previous two filtration methods.

How synthetic oil filters filter oil

Step One: Adsorption

In a one-on-one comparison the smooth exterior surface of synthetic glass fibers provides less surface than the fluffier cellulose fibers and thus has less adsorptive capabilities. However, the filter manufacturers make up for some of that loss by imparting an electrostatic charge to the fibers to attract and hold small particles. Overall, synthetic glass fibers don’t adsorb as many small particles as cellulose fibers.

Step two: Impingement

Due to their lack of a fluffy surface and soft structure, synthetic glass captures fewer particulate matter than a cellulose material

Step three: screening or direct interception

Because synthetic fibers are more uniform in size and can be formed into a denser mat, they can screen out smaller particles than cellulose materials. In other words, they have many more particle trapping voids that can trap and hold much smaller particles than cellulose

Comparing the pros and cons of cellulose and synthetic oil filters

Cellulose pros and cons

PRO: Cellulose is better at capturing small particles through adsorption and impingement than synthetic fibers.

PRO: Cellulose is organic and less costly than synthetic materials

CON: Cellulose fibers are unevenly sized so they be unpredictable in void (pores) sizes, filtration efficiency and useful life.

CON: Cellulose fibers can absorb moisture, increasing pressure drop and thus reducing oil flow rates, while also weakening the fabric

Synthetic filter pros and cons

PRO: Synthetic glass fibers are more uniform in diameter and smaller in size than cellulose fibers. So  filter manufactures can pack more fibers into the same or even smaller footprint, yet still provide better filtration than a conventional filter of larger size.

PRO: Synthetic glass fibers can filter out more of the engine-harming particle sizes than cellulose filters.

PRO: Synthetic fibers don’t break down, absorb moisture, or shed like cellulose fibers. So the filters last longer

PRO: The uniformity of fiber size makes for more predictable void sizing and thus more predictable filtration and filter life.

CON: Synthetic glass fibers, due to their smooth surface, are less effective at holding adsorbed and impinged particles for long time periods compared to cellulose fibers.

CON: Synthetic filters cost more than cellulose filters

For all these reasons, most oil filter manufacturers use a combination of cellulose and synthetic fibers in their “synthetic” filters. In other words, most synthetic filters are actually hybrid filters.

How oil flows through an oil filter

• Oil flows into the pleats, through the cellulose material and the filtered oil flows out through the center core.

cellulose oil filter oil flow

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