Pennzoil motor oils are made from the highest-quality base stocks available. The quality of the base oil depends on the crude oil from which it is derived and the refining process used to generate base stocks from crude oil. Base stocks are very complex substances that contain thousands of different hydrocarbon compounds. When scientists select base stocks for motor-oil formulation, they look for:

• Low volatility (volatility is the tendency to boil or evaporate)

• Low temperature fluidity (ability to flow and lubricate rapidly at startup)

• An optimum mix of compounds that provide resistance against thermal decomposition, sludge/deposit formation and a general resistance to any chemical change.

Base stocks are highly processed to reduce sulfur content, remove wax and impurities, and improve their resistance to deterioration in use. In recent years significant advances have been made in crude oil processing technologies that enable base oils of remarkable quality to be manufactured. At the forefront of these technologies is a process called Severe Hydrotreating, HT for short. While all other processes work by removing undesirable components, the HT process adds an important feature to the process: It actually chemically modifies many of the remaining components and in doing so converts a good motor oil base stock into a base stock with outstanding performance characteristics. When HT is combined with wax isomerization, a similar process, the effect is magnified.