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Base Oils Alan Outhwaite, Chevron Global Base Oils What is a base oil?

Base oil is the primary component in every finished lubricant. The amount ranges from 75% to over 99%, depending on the application. Base oil contributes to a lubricant’s thermal/oxidative stability, volatility and viscosity, which can be enhanced further with the use of additives.

How is base oil produced? Can be produced by a range of conventional (such as solvent extraction) and non-conventional (such as hydroprocessing) refining processes as well as a range of chemical synthesis routes depending on the type of base oil to be produced.

How many different types exist? There are many different types including paraffinic, naphthenic, synthetic, re-refined, bio-based, Gas -to-Liquids (GTL) and Coal-to-Liquids (CTL) base oils.

What does the grouping mean – I, ll, lll, lV, V? In 1993, in response to high quality base oils being produced from all hydroprocessing, the American Petroleum Institute (API) established a base oil classification system. By these standards, base oils in Groups II-IV and are considered premium base oils because of their purity and performance advantages. Group V encompasses everything else that doesn’t fit in Groups I-IV, including naphthenics that and are not generally regarded as highly pure.

Definition of API Base Oil Groups

How do the official and unofficial groupings compare? There are two often used unofficial groups, Group II+ and Group III+. They generally show a higher viscosity index (VI) than their official group base oils, for example, Group II+ has >110 VI, and Group III+ has > 130 VI. The higher VI usually indicates higher quality base oils.

What/how are base oils used?

In addition to automotive engine oils, base oils are used in metal working fluids, automatic transmission fluids, turbine oils, compressor oils, hydraulic fluids, greases, tractor hydraulic fluids, train engine lubricants and many more applications.

What is base oil viscosity? A measure of the resistance of a base oil to flow, it is temperature dependent.

Can base oil usage change/be adapted with time? Base oils have a significant impact on the viscosity of lubricants and other performance factors. As industry and OEM specifications become more stringent the selection of different viscosity grades and Groups of base oils used in formulations may be necessary.

What is the difference between naphthenic, paraffinic and synthetic base oils? This nomenclature reflects major chemical components in a base oil that can influence key performance properties, such as viscosity and oxidation stability. Naphthenic base oils generally have low VI, low pour point, but relatively high low temperature viscosity, moderate oxidation stability but higher solvency. In comparison, paraffinic base oils have good VI, good oxidation stability, good low temperature properties but lower solvency. Synthetic base oils provide good oxidation resistance, wider temperature range for applications, superior volatility and enable energy efficiency, but lower solvency and poorer lubricating properties.

What is the future for base oil production given the sustainability debate and need to protect the environment? Premium base oil quality contributes to emission control compatibility and energy conserving lubricants. More premium base oil capacity is being added to the market. Lubricants containing base oils are widely recycled. New processing schemes are producing premium base oils from renewable sources.

Group II and Group III have very similar properties with Group III having higher V.I. Source: API 1509, Appendix E, Section E.1.3




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