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 the vapor will light. Keep it above the hottest spot in the machine. Most oils sit between 120ºC (248ºF) and 280ºC (536ºF).

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: the base oil was built, not just distilled. Usually a higher viscosity index. That's the point.

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