Magnetic
A separator that uses a magnetic field to attract and hold ferromagnetic particles.

Magnetic filter
A filter element that, in addition to its filter medium, has a magnet or magnets incorporated into its structure to attract and hold ferromagnetic particles.

Magnetic plug
Strategically located in the flow stream to collect a representative sample of wear debris circulating in the system: for example, engine swarf, bearing flakes, and fatigue chunks. The rate of buildup of wear debris reflects degradation of critical surfaces.

Manifold
A filter assembly containing multiple ports and integral relating components which services more than one fluid circuit.

Manifold filter
A filter in which the inlet and outlet port axes are at right angles, and the filter element axis is parallel to either port axis.

Media migration
Material passed into the effluent stream composed of the materials making up the filter medium.

Medium
The porous material that performs the actual process of filtration. The plural of this word is “media”.

Metal Deactivator
A fuel or lubricant additive, which converts into an inactive form, the traces of metal (such as copper in fuels) and metal surfaces (such as copper in fuel lines) which, in the absence of the deactivator would catalyze gum formation and other oxidation.

Metal oxides
Oxidized ferrous particles which are very old or have been recently produced by conditions of inadequate lubrication. Trend is important.

Micrometre (µm)
See Micron.

Micron
A unit of length. One Micron = 39 millionths of an inch (.000039"). Contaminant size is usually described in microns. Relatively speaking, a grain of salt is about 60 microns and the eye can see particles to about 40 microns. Many hydraulic filters are required to be efficient in capturing a substantial percentage of contaminant particles as small as 5 microns. A micron is also known as a micrometre, and exhibited as µm.

Microscope method
A method of particle counting which measures or sizes particles using an optical microscope.

Mid-Continental crude
Petroleum oil obtained from the central regions of the United States (principally Oklahoma, Kansas, and North Texas), usually having characteristics between those of Pennsylvania and coastal oils.

Middle Distillate
One of the distillates obtained between kerosene and lubricating oil fractions in the refining processes. These include light fuel oils and diesel fuel.

Mil Spec
Military specifications; a guide in determining the quality requirements of products used by the military services, published by the United States Department of Defense.

Mineral oil
Oil derived from a mineral source, such as petroleum, as opposed to oils derived from plants and animals.

Miscible
Capable of being mixed in any concentration without separation of phases; e.g., water and ethyl alcohol are miscible.

Moly
Molybdenum disulfide, a solid lubricant and friction reducer, colloidally dispersed in some oils and greases.

Motor
A device which converts fluid power into mechanical force and motion. It usually provides rotary mechanical motion.

Motor Method- Motor Octane Number (MON)
A test for determining the knock rating, in terms of ASTM Motor Octane Numbers, of fuels for use in spark-ignition engines. The knocking tendency of the fuel is compared with those for blends of reference fuels of known octane number when run in the ASTM-CFR engine at 900 rpm, under standard operating conditions as prescribed in ASTM Method D 357.

MSDS
Material Safety Data Sheet

Multigrade oil
An oil meeting the requirements of more than one SAE viscosity grade classification, and may therefore be suitable for use over a wider temperature range than a single-grade oil.

Multipass or recirculation test
Filter perform-ance tests in which the contaminated fluid is allowed to recirculate through the filter for the duration of the test. Contaminant is usually added to the test fluid during the test. The test is used to determine the Beta-Ratio (q.v.) of an element.

Multipurpose Grease
A lubricating grease suitable to meet the individual requirements for chassis lubricant, bearing lubricant, joint lubricant, water-pump lubricant, and cup grease.


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