As open gear lubricants evolved, base oil selection became a crucial part in formulation. When selecting a base oil for OGLs, many variables need to be considered, such as: end use application, operating temperature and desired environmental profile base oil. Understanding the end use and whether they will be operating under fluid film, boundary or mixed lubrication conditions is very important. Traditionally, film thickness and strength were considered critical and drove the use of higher kinematic viscosity oils. One way to achieve higher kinematic viscosity base fluids is using polymers like polyisobutylene and synthetic base oils like Polyalphaolefins (PAO) as viscosity modifiers [5]. The use of high kinematic viscosity oils and polyisobutylene allows OGLs to better adhere to gears and prevent runoff during usage. More recently, new polymers like unique performance polymers (UPPs) have been found to be beneficial as viscosity modifiers and as base oils in other industrial gear oil applications (Ref. 5).