Lubricant fuel/energy efficiency is a critical feature for future lubricants. In order to provide step-out fuel economy while maintaining or improving other performance features for lubricants, base stocks with lower friction coefficients are needed.
A useful lubricant base stock is the PAO class of fluids. PAOs are highly stable, versatile and compatible with a wide range of materials, PAOs have many advantages over conventional mineral oil or high-quality Group III or Group III+ lubricants. More specifically, PAOs have superior viscosity index (VI), low temperature properties (CCS (crankcase simulation), MRV (mini-rotary viscometer), and the like), low pour points, good additive response and complete miscibility with conventional mineral oil. PAOs are considered by the industry to be the best of hydrocarbon-type lubricants.
Another useful lubricant base stock is the PAG class of fluids. Advantages of PAG fluids include high VI, good lubricity (in hydrodynamic, mix, and boundary lubrication conditions) and excellent cleanliness. PAG fluids have numerous drawbacks. PAG fluids are not miscible or compatible with conventional mineral or hydrocarbon-based lubricants. PAGs are polar and have very low friction/traction for energy efficiency. PAG fluids are water-soluble, which results in severe corrosion problem. Some PAG fluids also have paint and/or seal compatibility problem.