Naphthenic

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

Needle bearing

Rolling types 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)

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 fibres.