Glossary of Common Oil Terms

AW: Anti-Wear, usually contains additives (often zinc-based) to reduce the amount of wear

Centipoise (cP), the unit of dynamic viscosity

Centistoke (cSt), the unit of kinematic viscosity (most common for oils)

EP: Extreme Pressure, usually for gears with high load

Flash Point: Lowest temperature at which the oil gives off flammable vapors. Measure in ºC or ºF, most oils are between 120ºC (248ºF) and 280ºC (536ºF). The Flash Point must be higher than the highest temperature in the equipment.

ISO: International Organization for Standardization. This group publishes standards and references for oils (notably the ISO Grade)

ISO Grade, sets the standard for oil. Given as ISO ##, the viscosity of the oil at 40ºC must be within +/- 10% of the ##. More information is available in the standards conversion chart

LICC: Lubricant-Induced Copper Corrosion, the effect when components in an oil cause copper to corrode

Pour Point: Lowest temperature at which the oil still flows like a liquid. Measured in ºC or ºF, most oils are between -60ºC (-76ºF) and -10ºC (+14ºF). The Pour Point must be lower than the lowest temperature the equipment will start operating in.

R&O: Rust and Oxidation, usually means the oil has some rust preventing additives

SAE: Society of Automotive Engineers, an organization that publishes oil standards for automotive applications. More information is available in the standards conversion chart

SUS: Saybolt Universal Seconds, an older metric for determining oil viscosity, largely replaced by ISO

Synthetic oil, means an oil where the Base Oil (the bulk of the oil) has been synthesized, not just distilled. The synthesis is a chemical or physical modification of the base product, and usually results in an oil with a higher Viscosity Index

Viscosity: Measures a fluid’s resistance to flow (thicker, like honey, is higher). Measured in centi-Stokes (cSt), most oils are generally between 2 - 2000 cSt. Faster equipment needs lower viscosity oils

Viscosity Index: Measures how much the viscosity changes with temperature. No units, but most oils are generally 90-190, usually around 100. Equipment with wide operating temperatures need a higher Viscosity Index. Learn More or Calculate