What the Heck is
a Micron, Anyway?

A micron, short for micrometer, is a unit of measurement equal to one millionth of a meter. A micron is actually 0.000039 of an inch.

To give you an idea what we are talking about here, the period at the end of this sentence is about 397 microns. The eye of a needle is usually elongated, but is 749 microns wide. A human hair is 40 to 120 microns in diameter. A postage stamp is more than 25,000 microns long.

Particle Size of Contaminants in Microns The critical size is 5 to 20 microns. Contaminants in this range are larger than the finest tolerances in your engine, but too small for full flow oil filters to remove, causing 60% of wear.

What does this mean when considering engine wear? The full flow filter, the one that comes on your car, must maintain a constant supply of oil to the engine. Motor oil picked up out of the crank case reservoir by the oil pump is first directed to the oil filter. Then, the motor oil passes to the rest of the engine to do its job of lubrication, transport dirt and wear material away from moving engine parts, and absorb heat from moving parts caused by friction or the combustion process. If the oil filter does too good of a job removing contaminants, it will "blank out" and not allow oil to flow through the filter. As a result of the pressure drop from one side of the filtering media to the other, the by-pass safety valve in the filter will open allowing oil to go around the filtering media, but still supplying oil to the engine. This means the oil does not get cleaned and the dirt and other contaminants are allowed to accumulate in the oil, increasing wear. Other problems may result if these contaminants accumulate in places like behind the piston rings. This situation will cause the rings to loose their seal, allowing oil to get past the rings and into the combustion chamber, resulting in oil use.

On the other hand, if the filter does not filter well enough to minimize wear, then the engine will wear out sooner. What's a guy to do???

Filters are measured by their "beta" rating. This is not a universal standard, but is simply stated as the smallest particle size that will be removed 98% efficient with one pass of the oil through the filter. Particles smaller will take more passes or will not be removed from the oil at all, and larger particles are removed from the oil flow 100% of the time. Most full flow filters, depending on quality (and reflected in price), will remove contaminants at this "beta" efficiency that are larger than between 25 and 45 microns. This is usually sufficient to give reasonable useful life to the filter and the engine's critical main and rod bearings. The tolerances on these main and rod bearings can be anywhere from two to four thousandths of an inch (0.002 to 0.004"). Considering that the crank is centered in the bearing journal, that means the thickness of the oil that lubricates and supports the rotation of the crank is between one and two thousandths. One thousandth of an inch equates to 25 microns, so a better quality full flow filter will do a good job protecting your rod and main bearings from normal wear.

Where the problem comes in is in other critical tolerances, such as the cam lobe to lifter, ring clearance to the cylinder wall, or the valve train components. These areas can be as small as 5 microns. These clearances are only the thickness of the lubricants between the metal components. Fully 60% of wear in an engine occurs in these areas as a result of contaminants that are larger than 5 microns, but too small for the 25 micron full flow filter to remove and hold out of the system.

This is why supplemental filtration that can remove contaminants in the 5 to 20 micron range is so important. Many by-pass filters will remove contaminants down to 10 microns, but the AMSOIL By-Pass Filter has been shown to have a beta rating of 3 microns, and will remove some contaminants down to 1/10 of a micron. As a result, the 60% of wear which results from the contaminants in the 5 to 20 micron range can be virtually eliminated by utilizing an AMSOIL By-Pass oil filter in conjunction with a full flow oil filter.