NAFTA
North American Free Trade Agreement

Naphthenic
A type of petroleum fluid derived from naphthenic crude oil, containing a high proportion of closed-ring methylene groups.

Needle bearing
A rolling type of bearing containing rolling elements that are relatively long compared to their diameter.

Neutralization number
A measure of the total acidity or basicity of an oil; this includes organic or inorganic acids or bases or a combination thereof (ASTM Designation D974-58T)

Neutral Oil
Light overhead cuts of lubricant stocks. Neutral oils are the basis for most commonly used automotive lubricants.

NLGI Number
One of a series of numbers classifying the consistency range of lubricating greases, based on the ASTM cone penetration number. The National Lubricating Grease Institute (NLGI) grades are in order of increasing consistency (hardness).

Newtonian fluid
A fluid with a constant viscosity at a given temperature regardless of the rate of shear. Single-grade oils are Newtonian fluids. Multigrade oils are NON-Newtonian fluids because viscosity varies with shear rate.

Nitration
Nitration products are formed during the fuel combustion process in internal combustion engines. Most nitration products are formed when an excess of oxygen is present. These products are highly acidic, form deposits in combustion areas and rapidly accelerate oxidation.

Nominal filtration rating
An arbitrary micrometer value indicated by a filter manufacturer. Due to lack of reproducibility this rating is deprecated.

Non-Newtonian fluid
Fluid, such as a grease or a polymer-containing oil (e.g., multi-grade oil), in which shear stress is not proportional to shear rate.

Nonwoven medium
A filter medium composed of a mat of fibers.


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