Today gear drive operations have several options when selecting the proper lubricant for their gearboxes. As in the past, the primary lubricant used for gearbox lubrication is mineral oil. But with the advances in technology, synthetic hydrocarbons (PAOs) and polyglycols show very specific advantages in certain applications. With gear drives becoming more and more precise, it is now also to the benefit of the gear operator to verify that he or she has the proper additive package and viscosity in the lubricant selected. Fig. 1 shoes that a gear oil is a combination of a base oil and specific additives. The base oils can be either mineral oil, a synthetic or even in some cases a combination of the two.