Lubricating oils are a necessary component for a wide array of machinery, serving to reduce friction and wear by separating surfaces, both metallic and plastic, which are moving with respect to each other. They are also carriers for various other specialty chemicals that inhibit corrosion, fight oxidation, and modify viscosity among other properties. It is critical to understand the specific end use of the fluid as the requirements will vary depending on the application. It is imperative that these individual chemicals and formulated fluids undergo rigorous testing throughout the design process to ensure compatibility and reduce failure risks when the oil and equipment are placed into service. These tests will serve to identify proper specialty chemical additions, ensure appropriate physical characteristics for the designed purpose, verify fluid stability at low and high temperatures and varying humidity, evaluate oxidative stability, and determine wear and load carrying capacities. Once fluids can meet industry and customer defined performance requirements in the various laboratory tests, full engine and rig tests will be employed for a better measure of performance in high stress conditions. Ultimately though, the true measure of a fluid's performance can only be quantified in fleet testing, where the fluids are subjected to routine use in real world conditions. As the design of the machinery and demands on the lubricating fluid change, the chemistry of the lubricant and the testing used must be adapted to meet the new performance requirements.