Oil filters do a poor job at filtering out particles smaller than 25 microns, and these particles will cause engine wear over time

Tests show that most normal wear on an engine comes from particles two to 10 microns in size that pass freely through oil filters. Most engine manufacturers specify oil filters that have an effective average efficiency of around 25 microns (plus or minus five microns) in particle size for warranty purposes. But this does not mean everything above 25 microns is filtered out. Far from it! Laboratory test data reveals that a percentage of particles 40 and 50 microns in size still pass through most filters to some degree.

Magnetic filtration, where a magnet is added to the oil filter to pull out fine iron and other particles, is a very inexpensive way to improve filter performance. In my opinion, magnetic filtration is the key to effective filtration and the preservation of newer engines that are built to finer tolerances. As long as the maximum-sized particles in the oil are even close in size to engine tolerances, engine wear will occur.

David R. Staley of General Motors reported that, “Abrasive engine wear can be substantially reduced with an increase in single pass efficiency. Compared to a 40-micron filter, gasoline engine wear was reduced by 50 per cent with 30-micron filtration. Likewise, wear was reduced by 70 per cent with 15-micron filtration. Controlling the abrasive contaminants in the range of two to 22 microns in the lube oil is necessary for controlling engine wear.”

Magnetic filtration is the only practical method of achieving this microscopic level of oil filtration at a low cost.

Two options for magnetic filtration

Magna-Guard (www.magna-guard.com)makes a magnet that you insert into the centre tube of the filter. You insert the magnet through the large thread hole and then push it back to the far end of the tube. I found it is almost impossible to get one out once it’s properly installed. Be sure not to just drop it in the hole, as some tubes are plastic, aluminum or stainless steel and are not magnetic material.

Magna-Guard used Titan Labs in Denver, Colorado to analyze the effectiveness of its magnetic centre tube insert. It does a good job of removing even the tiniest particles. It removed 77 per cent of iron particles of 0.5 microns and 86 per cent of magnesium particles. It also

removed large percentages of sodium, silicon (dirt) and other particles, many of them not normally magnetic. How? Microscopic nonmetallic particles become slightly electrically polarized as they pass through an extremely strong magnetic field. As these slightly polarized microscopic particles circulate, they have a tendency to conglomerate just like a pile of

small magnets would. As the particle clump grows, its field becomes stronger since it continually passes through the filter and magnetic field, until it is finally drawn into the magnet.

Your other option comes from FilterMAG ( www.filtermag.com). It molds a series of strong neodymium magnets into a semicircular band that is installed on the outside of spin-on filters. FilterMAG makes 10 different sizes to fit almost any filter. Because the magnets are arranged in a semi-circle, the magnetic force gets focused toward the centre of the circle, similar to the way an optical lens focuses light to a point. Concentrating the strength of the magnetic field into a small area creates a super magnet, drawing particles to the side of the filter.

The larger the filter, the harder it is to remove the FilterMAG. A pusher screw is provided to pry the filter back far enough to get your fingers into the gap and rotate the magnet off the filter.

FilterMAG used Predictive Maintenance Services, Inc. in Uhrichsville, Ohio to analyze the effectiveness of its external semi-circular filter. Results showed that FilterMAG magnets remove 83 per cent of particles two microns and bigger. Keep in mind that all this contamination normally passes through OEM filters and is the primary wear material that needs to be removed.

Other magnets

You may have seen the magnetic oil pan drain plugs. This type of plug was the first application of magnetic filtration and has been used in engines, transmissions and differentials to remove harmful wear metal.

The only oil filter I could find that uses “built-in” magnetic filtration is a Kubota tractor filter that is factory installed and used on their new engines during break-in. Kubota uses a circular donut filter that overlaps the base plate holes to insure all oil passing into the filter passes very close to the magnet.

You may ask whether just any magnet will work for this application. The answer is no. Regular store-bought magnets are more for toys and crafts. Also, nonindustrial magnets have a tendency to lose their magnetism when heated to around 200 F, so their service life would be very short. Using a magnet that is not specifically designed for this purpose could cause you to lose a magnet into your oil galley!

There are a few other types of magnets that work on oil filters, but I don’t think they will be as effective as Magna-Guard and FilterMAG.

Paul Dilger is a retired instructor in the field of farm machinery. He founded the Ag Safety Institute at Cal Poly State University. He currently farms at Santa Margarita, California.

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