Extreme-pressure gear lubricants, or EP gear lubes, are required in gearboxes that operate at extremely high temperatures and pressures and are referred to as heavily-loaded gear drives. These oils are specially formulated with additive technology designed to minimize deposit formation and keep gearboxes exceptionally clean. These machine components work at very high temperatures and pressures so it is required that the lubricants implemented contain EP additives, which help to minimize wear.
AGMA 2 oils are also classified as ISO VG 68 oils. AGMA 2 EP oils have the same relative viscosity as AGMA 2 oils, however, they are marked to show they contain extreme-pressure additives, which are not always compatible with certain yellow metal machine components. These oils have a midpoint kinematic viscosity of 68 mm2/s, also referred to as centistokes (cSt). The midpoint is derived by taking the average of both the minimum and maximum kinematic viscosities. In the case of ISO VG 68 oil (also AGMA 2 oil), those numbers are 61.2 cSt and 74.8 cSt, respectively. These numbers refer to the standard testing mechanisms used to determine how much resistance to flow (i.e. viscosity) these oils demonstrate.