Particle Capture Principles

The FilterMags installed on your filters have the extremely high magnetic power necessary to attract tiny particles moving in fluids with high flow rates. The particle size and dwell time determine how many FilterMags are needed to be effective in protecting your equipment.


Engine Oil

Engine oil recirculates through filters presenting a continuous opportunity for Filtermag to capture particles. Two FilterMags expose all of the recirculating oil to FilterMag’s magnetic fields. We can get technical.


Hydraulic Fluid

Hydraulic systems have high-tolerance finished mechanical surfaces. Therefore, the wear particles generated are smaller than what is found in engine oil. The smaller the particles, the more difficult it is to attract them from the flowing oil. Additional FilterMags are needed to increase the particle dwell time. Install in stacked rings near the threaded end of the filter or filter canister. We can get technical.


Engine Fuel

The FilterMags have a one pass opportunity to capture particles in fuel. Six FilterMags are required. Install in three stacked rings near the threaded end of the filter. We can get technical.



Two FilterMags are installed in a ring near the threaded end of a spin-on filter, or near the open end of a canister filter allowing enough clearance to service the filter. Caution: FilterMag XTs are installed permanently.

Four or more FilterMags are installed in stacked rings, staggered 90-degrees, near the threaded end of a spin-on filter, or near the open end of a canister filter allowing enough clearance to service the filter.


Correct Vertical Placement

FilterMags should be mounted approximately 1” below the threaded end of the oil filter. This ensures all oil flowing into the filter will be exposed to FilterMag’s magnetic force as it enters the filter.


Incorrect Installation

All CT4.9s in this photo are installed at the bottom of each filter. Much of the oil entering and exiting the filter will have limited exposure to the magnetic filtration, greatly reducing efficacy.

Correct FilterMag CT Sizing Guide


Proper FilterMag selection is based on filter diameter (see Industrial Products pages for size ranges). However, there are visual clues that the wrong FilterMag has been selected for a particular application.


This looks like a good fit, but it’s not.


The FilterMags are too large for the filter and not making complete contact.

Are they are too large?

Although this looks like a good fit, it’s not. This filter diameter is 4.3”. CT4.9s require a minimum diameter of 4.4”. That 0.1” in diameter difference prevents the FilterMags from making complete contact to the outside wall of the oil filter.

The best indicator of an incorrect fit is when two FilterMags are butting against each other.

Because the two CT4.9s are butting against each other, they create a diameter larger than the filter. This creates a gap between the FilterMags and the filter.

This 0.1” gap is very significant; it will severely limit the FilterMag’s effectiveness, and reduce the magnetic bond securing the FilterMags to the filter.


Push the FilterMag to cause it to flex and snap securely to the filter.


Proper installation will result in a space between two opposing FitlerMags.

Do the FilterMags appear too small?

FilterMag CTs and XTs are flexible over a range specified. Installing CT3.8s to this filter requires a slight push forcing the CT3.8s to flex and snap securely to the filter.