- Base Stock
- Basics
What are base stocks?
Base stocks are the key building blocks of lubricants and greases, A base stock is a single lubricant component produced by a single manufacturer and oil marketers or formulators mix them to make the finished products.
What are base oils?
The terms base stocks and base oils are often used interchangeably but there are differences, A base stock is a single product usually defined by its viscosity grade, A mixture of one or more base stocks in a finished lubricant is a base oil, A base oil is always defined in the context in the formulated lubricant, Base oil properties can vary depending on their API group.
What is the API base stock classification system?
The API classification system categorizes base stocks into numbered groups, Groups I, II, III, IV and V, The first three are refined from crude oil, There are a few Group III base stocks that are produced from bio-based feedstocks or natural gas, Group IV base stocks are fully synthetic polyalphaolefins or PAOs, Group V is comprised of base stocks that do not fall into the other groups.
Why are there API base stock groups?
API base stock groups were first defined as a means to develop interchange guidelines in engine oils, The initial idea behind the base stock groups was that the manufacturing process would form a rough framework for considering interchange thus originally, Solvent refined base stocks were considered Group I, hydroprocessed base stocks were considered Group II and all other base stocks including chemically derived base stocks were considered Group III.
How do base stock properties vary between groups?
✅ Group II have more saturates and less sulfur than Group I. They typically have better low temperature properties and are more oxidatively stable than Group I base stocks.
✅ Group III base stocks have higher VI’s than Group I or II by definition and are even more oxidatively stable than Group II. Group III base stocks typically span a narrower range of viscosities than Group I or Group II.
✅ Group IV is generally very oxidatively stable and has excellent low temperature performance. For these reasons, it is generally used only in the highest performing lubricants.
✅ Group V are often blended with other base oils to affect the finished lubricant’s properties.
All base stock groups have properties that make them suitable in a specific range of applications.
✅ Group III base stocks have higher VI’s than Group I or II by definition and are even more oxidatively stable than Group II. Group III base stocks typically span a narrower range of viscosities than Group I or Group II.
✅ Group IV is generally very oxidatively stable and has excellent low temperature performance. For these reasons, it is generally used only in the highest performing lubricants.
✅ Group V are often blended with other base oils to affect the finished lubricant’s properties.
All base stock groups have properties that make them suitable in a specific range of applications.
Can base stock properties and performance vary within a group?
While the API group definitions provide a framework for classifying base stocks, base stocks within a specific group can have significantly differing properties, Specifically viscosity index, Low temperature viscosity, Volatility and saturates level, Not all base stocks within a given API group can be expected to provide the same level of performance in a formulated lubricant, The most reliable method of predicting performance in field applications is by actual bench, Rig and engine testing.
What are paraffinic base stocks?
Paraffinic base stocks and paraffinic base oils are produced from paraffinic crude oil, Which gives a good yield of stable base stocks with a high viscosity index.
What are naphthenic base stocks?
Naphthenic base stocks and napthenic base oils are produced from naphthenic crude, They are less stable and have a lower viscosity index than paraffinic base oils, However, They generally have outstanding low temperature performance characteristics, Transformer oils are often formulated with naphthenic base stocks.
What are synthetic base stocks?
There is no generally accepted definition of a synthetic base stock or synthetic base oil. In the U.S, The government considers “Synthetic” to be a marketing term characterizing the formulated lubricant while in Germany, Synthetic base stocks are defined by law to be polyalphaolefins or esters, Many oil marketers consider lubricants formulated with significant concentrations of Group IV and/or Group III base stocks as synthetic, Most Group III base stocks are refined from crude oil streams.
What is bright stock?
Bright stock is a Group I base stock derived from deasphalted vacuum resid, It is used where high viscosity or solvency is required.
What is a base stock slate?
The API defines a base stock slate as a series of base stocks of the same group from the same manufacturer with different viscosities, Base stocks within a slate may be substituted for one another to achieve the same blended viscosity without the need for additional engine testing, For example, An oil marketer could substitute EHC™ 45 and EHC™ 65 for EHC 50™ in a qualified formulation without the need for engine testing.
What is base oil interchange ( BOI )?
Base oil interchange is a set of guidelines that allows the substitution of base stocks belonging to a specific base stock slate into a formulation approved with base stocks belonging to a different slate.
- Base Stock Applications
What are some base oil uses?
Base oils are used to make various lubricants and greases across all industries, Base oils can represent from 75% to 99% of a finished lubricant, These might be automotive engine oil, Grease or metal processing fluids.
What are base stock manufacturers? What are oil marketers?
A base stock manufacturer is the entity that defines the product identifier, Specifications and quality management system of base stock(s) which are produced at one or more manufacturing sites.
An oil marketer is the marketing organization responsible for the integrity of the brand name and the representation of a branded product in the marketplace, Oil marketers own the product specifications of a formulated lubricant and are responsible for the representation of a lubricant’s performance, An oil marketer may contract with a lubricant blender to blend products meeting their specifications.
An oil marketer is the marketing organization responsible for the integrity of the brand name and the representation of a branded product in the marketplace, Oil marketers own the product specifications of a formulated lubricant and are responsible for the representation of a lubricant’s performance, An oil marketer may contract with a lubricant blender to blend products meeting their specifications.
What are the specific uses of Group I base stocks?
Group I base oils are the least severely refined and make up the bulk of the base oil market, They are generally used in broad applications such as industrial lubricants, Gear oils and marine.
What are the specific uses of Group II base stocks?
Group II base oils have less sulfur and are usually more stable than Group I base oils, Which gives them a wider range of uses in high performance situations, They are often used in automotive and heavy duty engine oils as well as in industrial lubricant and other applications.
What are the specific uses of Group III base stocks?
Group III base oils are used primarily in higher tier, Low viscosity engine oils although they have found increasing use in premium industrial lubricants, The low viscosity of Group III base stocks limits their applicability to a broad range of industrial lubricant applications.
What are the specific uses of Group IV base stocks?
Polyalphaolefin Group IV base stocks span a range of viscosities and are used in a variety of applications, Group IV stocks are generally used in flagship type products demanding the highest level of performance.
- Base Stock Production
How are base stocks produced?
The production method varies by base stock group, Additional complexity exists for base stocks produced from used oil, The first step in the production of “ virgin ” base stocks, Yhose produced from crude oil is distillation, Distillation is used to separate molecules based on boiling point into streams suitable for upgrading to fuels and those which can be upgraded to lubricant base stocks, After distillation, Various steps involving separation and/or molecular transformation are used in the production of base stocks.
How are Group I base stocks produced?
Group I base stocks are conceptually the simplest to manufacture and are produced by separating molecules by solvent-assisted processes, The two primary processes involved in the manufacture of Group I base stocks are solvent extraction, Which removes polar molecules thus improving the oxidative and thermal stability of the base stock and solvent dewaxing, which removes wax and improves the low temperature fluidity of the base stock.
How are Group II and Group III base stocks produced?
Group II and Group III base stocks are generally produced from distilled crude oil streams upgraded through high pressure catalytic processes involving hydrogen, The first step in the process involves hydrotreating and frequently hydrocracking, Hydrotreating saturates aromatic species in the feed stream and removes virtually all sulfur and nitrogen from the feed, Hydrocracking involves further conversion of hydrocarbons in the feed primarily to boost the viscosity index of the resultant base stock, Dewaxing and hydrofinishing via catalytic processes follows with the goal of converting wax species, Preferably by isomerization, to reduce the pour point of the base stock improve its low temperature fluidity and to improve its oxidative stability, Group III base stocks differ from Group II in that they generally originate from high quality feeds and may require more severe processing.
Some Group III base stocks are produced by natural gas or coal conversion to synthesis gas, Carbon monoxide and hydrogen, Which is converted by the Fischer-Tropsch process and subsequently upgraded in a way similar to convention Group III base stocks.
Some Group III base stocks are produced by natural gas or coal conversion to synthesis gas, Carbon monoxide and hydrogen, Which is converted by the Fischer-Tropsch process and subsequently upgraded in a way similar to convention Group III base stocks.
What factors affect the current base oil price?
Since base oils are most often made from crude oil, An increase in the price of oil will cause a base oil price increase, This can mean base oil prices vary between base oil suppliers.