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NATURAL GAS - naturally occurring mixture of gaseous saturated hydrocarbons, consisting of 80-95% methane (CH4), lesser amounts of propane, ethane and butane, and small quantities of non-hydrocarbon gases (e.g., nitrogen, helium). Natural gas is found in sandstone, limestone, and other porous rocks beneath the earth’s surface, often in association with crude oil. Because of its high heating value and clean-burning characteristics, natural gas is widely used as a fuel. The heavier hydrocarbons in natural gas can be extracted, through compression or absorption processes, to yield LPG (propane or butane), natural gasoline, and raw materials for petrochemical manufacture. See natural gas liquids.

NATURAL GAS LIQUIDS - hydrocarbons extracted from natural gas: primarily LPG (propane or butane) and natural gasoline, the latter being commonly blended with crude-derivative gasoline to improve volatility. Natural gas liquids can be separated from the lighter hydrocarbons of natural gas by compression (the gas is compressed and cooled until the heavier hydrocarbons liquefy) or by absorption (the gas is mixed with a petroleum distillate, such as kerosene, which absorbs, or dissolves, the heavier hydrocarbons).

NEOPRENE RUBBER (CR) - synthetic rubber, a chloroprene polymer, with excellent resistance to weather, oil, chemicals, and flame. Widely used for electrical cable insulation, industrial hose, adhesives, shoe soles, and paints.

NEUTRAL OIL - lubricant basestocks which are light overhead cuts from vacuum distillation units. Named for their SUS viscosity at 100°F, having viscosities ranging from about 13 to 130 cSt at 40°C. They are usually solvent or clay treated, but not refined with acid or alkali. Most commonly used to formulate automotive and commercial crankcase lubricants.

NEUTRALIZATION NUMBER - also called neut number, an indication of the acidity of alkalinity of an oil; the number is the weight in milligrams of the amount of acid (hydrochloric acid {HCL}) or base (potassium hydroxide {KOH}) required to neutralize one gram of the oil, in accordance with test method ASTM D 664 (potentiometric method) or ASTM D 974 (colorimetric method). Strong acid number is the weight in milligrams of base required to titrate a one-gram sample up to a pH of 4; total acid number is the weight in milligrams of base required to neutralize all acidic constituents. Strong base number is the quantity of acid, expressed in terms of the equivalent number of milligrams of KOH, required to titrate a one-gram sample to a pH of 11; total base number is the milligrams of acid, expressed in equivalent milligrams of KOH, to neutralize all basic constituents. If the neutralization number indicates increased acidity (i.e., high acid number) of a used oil, this may indicate that oil oxidation, additive depletion, or a change in the oil’s operating environment has occurred.

NEWTONIAN FLUID - fluid, such as a straight mineral oil, whose viscosity does not change with rate of flow. See shear stress.

NITRATION - the process whereby nitrogen oxides attack petroleum fluids at high temperatures. Nitration often results in viscosity increase and deposit formation.

NITROGEN OXIDES (NOx) - emissions, from man-made and natural sources, of nitric oxide (NO), with minor amounts of nitrogen dioxide (NO2). NOx are formed whenever fuel is burned at high temperatures in air, from nitrogen in the air as well as in the fuel. Motor vehicles and stationary combustion sources (furnaces and boilers) are the primary man-made sources, although automotive emission controls are reducing the automobile’s contribution. Natural emissions of NOx arise from bacterial action in the soil. NOx can react with hydrocarbons to produce smog. See catalytic converter, emissions (automotive), hydrocarbon emissions.

NLGI (NATIONAL LUBRICATING GREASE INSTITUTE) - trade association whose main interest is grease and grease technology. NLGI is best known for its system of rating greases by penetration.

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. See Brookfield viscosity.

NORMAL PARAFFIN - hydrocarbon consisting of unbranched molecules in which any carbon atom is attached to no more than two other carbon atoms; also called straight chain paraffin and linear paraffin.