It is generally accepted that synthetics outperform conventional oils, but many people don’t understand why. The differences begin at a molecular level.
Conventional lubricants are refined from crude oil. Contaminating elements such as sulfur, nitrogen, oxygen and metal components such as nickel or vanadium are inherent to crude oil and cannot be completely removed through the refining process. The oil refining process separates the various types of molecules in the oil by weight, leaving molecules similar in weight but dissimilar in structure.
Synthetic lubricants, on the other hand, are chemically engineered to form pure lubricants. Synthetic lubricants contain no contaminants or molecules that don't serve a designed purpose. They are made from molecules that are saturated with a higher percentage of carbon- hydrogen bonds, leaving fewer sites to which other, harmful molecules can attach and attack the molecular composition of the oil. In addition, their smooth, uniform lubricating molecules slip easily across one another.
In short, synthetics' versatility and pure, uniform molecular structure impart properties that provide better friction-reduction, optimum fuel efficiency, maximum film strength and extreme-temperature performance conventional lubricants just can't touch.