Popular terms is to use mineral oil esters (Easter) or polyolefins (PAOoly-Alfa-Olefine) to replace, with reference again and additives, synthetic oil is, and if the whole base oil with esters or polyolefins substituted, it is called fully synthetic oil (Fully-synthetic oil) if only with a part called a semi-synthetic oil (partial-synthetic oil).

 There are many so-called full synthetic oil, it is not a wholly synthetic real scientific sense, most of them belong to the third category of highly refined mineral oil (GroupIII), and full synthetic oil true scientific sense should crude oil the methane gas or natural gas dispersed out of ethylene, propylene, and then by polymerization, catalysis of chemical reactions before refining complex larger than the molecular basis of the composition of the liquid, called PolyAlphaOlefins (PAO), there is alcohol and fatty acid based materials, chemical condensation reaction of synthetic esters full synthetic oil.

 Prior to 1999, generally only to 100% PAO or ester as lubricating base oil will be printed on the packaging "Full Synthetic" (total synthesis) of these two English words. In 1999, Castrol Mobil allegations should not be on the product to third base oils made in India on "Full Synthetic" words. US consumer advocacy organization Better Business Bureau ruled that the allegations were not due to "Full Synthetic" on the packaging is the marketing of words, rather than scientific words. Since then, many lubricant manufacturers have said their products to third base oils made of full synthetic oil.