Synthetic oil

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A sample of synthetic motor oil Motor oil.JPG
A sample of synthetic motor oil

Synthetic oil is a lubricant consisting of chemical compounds that are artificially modified or synthesised. Synthetic lubricants can be manufactured using chemically modified petroleum components rather than whole crude oil, but can also be synthesized from other raw materials. The base material, however, is still overwhelmingly crude oil that is distilled and then modified physically and chemically. The actual synthesis process and composition of additives is generally a commercial trade secret and will vary among producers. [1]

Contents

Synthetic oil is used as a substitute for petroleum-refined oils when operating in extreme temperature. [2] Aircraft jet engines, for example, require the use of synthetic oils, whereas aircraft piston engines do not. [3] Synthetic oils are also used in metal stamping to provide environmental and other benefits when compared to conventional petroleum and animal-fat based products. [4] These products are also referred to as "non-oil" or "oil free".

A polyalcanoate synthetic oil is widely used to lubricate pendulum clocks.

Types

Full

Some synthetic oils are made from Group III base stock, some from Group IV while other synthetic oils may be a blend of the two. Mobil sued Castrol and Castrol prevailed in showing that their Group III base stock oil was changed enough that it qualified as full synthetic. Since then American Petroleum Institute (API) has removed all references to synthetic in their documentation regarding standards. "Full synthetic" is a marketing term and is not a measurable quality.

Group IV: PAO

Poly-alpha-olefin (poly-α-olefin, PAO) is a non-polar polymer made by polymerizing an alpha-olefin. They are designated at API Group IV and are a 100% synthetic chemical compound. It is a specific type of olefin (organic) that is used as a base stock in the production of most synthetic lubricants. [5] An alpha-olefin (or α-olefin) is an alkene where the carbon-carbon double bond starts at the α-carbon atom, i.e. the double bond is between the #1 and #2 carbons in the molecule. [6]

Group V: Other synthetics

Group V base oils are defined by API as any other type of oil other than mineral oils or PAO lubricants.

Esters are the most famous synthetics in Group V, which are 100% synthetic chemical compounds consisting of a carbonyl adjacent to an ether linkage. They are derived by reacting an oxoacid with a hydroxyl compound such as an alcohol or phenol. Esters are usually derived from an inorganic acid or organic acid in which at least one -OH (hydroxyl) group is replaced by an -O-alkyl (alkoxy) group, most commonly from carboxylic acids and alcohols. That is to say, esters are formed by condensing an acid with an alcohol.

Many chemically different "esters" due to their polarity and usually excellent lubricity are used for various reasons as either "additives" or "base stocks" for lubricants. [6]

Polyalkylene glycol (PAG) synthetic oil
Industrial PAG

The terms polyalkylene glycol and polyglycol are used interchangeably. [7]

Synthetic lubricants are about 4% of the lubricants market. PAGs are about 24% of the synthetic lubricants market.

Ethylene is the basic raw material used to make the synthetic lubricant polyglycols oils. When ethylene and propylene react with oxygen we obtain ethylene oxide (EO) and propylene oxide (PO), from which the polyalkylene glycols are produced by means of polymerization. Polyalkylene glycols are usually made by combining ethylene oxide and/or propylene oxide with an alcohol or water.

The mixing ratio between EO and PO, plus the oxygen bonded in the chemical structure, crucially affect the behavior of polyglycols. The gear industry predominantly uses polyglycols with an EO/PO ratio of 50:50 to 60:40, which exhibit very similar behavior. The polyglycols featuring this composition are also generally referred to as water soluble polyglycols. [8]

Polyalkylene glycol base oils are formed by reacting an alcohol with one or more alkylene oxides: Propylene oxide provides water insolubility, Ethylene oxide provides water solubility.

PAG properties

PAGs offer properties that include: high lubricity, polarity, low traction properties, high viscosity index, controlled quenching speeds, good temperature stability and low wear. They are available in both water soluble and insoluble forms. [9]

PAG uses

PAGs are commonly used in quenching fluids, metalworking fluids, gear oils, chain oils, food-grade lubricants and as lubricants in HFC type hydraulics and gas compressor equipment. [9] PAG lubricants are used by the two largest U.S. air compressor OEMs in rotary screw air compressors. [7] PAG oils of different viscosity grades (usually either ISO VG 46 or ISO VG 100) are often used as compressor lubricants for automotive air conditioning systems employing low global warming potential refrigerants.

PAG advantages

PAGs are available in a wide range of viscosity grades and additive packages for a variety of uses. Some PAGs properties such as water solubility are not commonly provided by other synthetic lubricants, such as polyalphaolefins (PAO).

PAGs prevent sludge and varnish from developing at high temperatures. PAGs have viscosity indexes that are higher than PAOs. [10] [11] [12]

In large gears, PAG lubricant yielded lower friction than PAO lubricant. [13]

PAG oils are polar, which means that an oil film easily develops upon all moving metal parts, reducing startup wear.

PAGs can be highly biodegradable, particularly the water-soluble PAGs. [14]

PAGs perform better than in extreme weather condition. [15]

PAG disadvantages

PAGs are not compatible with mineral oils, most seals, paints, varnishes. [16] [7]

Synthetic oil is more expensive than mineral oils. [17]

PAG seal compatibility

PAG is usually compatible with fluorocarbon-based fluoroelastomer materials and vinyl methyl silicone (VMQ) silicone rubber.

PAG acts as a solvent and dissolves and removes the mineral grease which causes slower motions, air leaks, and can stop 4-way valves from operating. [18] [19]

Natural rubber, Buna-N, and most regular seals are incompatible with PAG oils, especially seals coated in mineral grease. PAG oils can cause seals to shrink or swell, thus causing severe leakage or seizure of the seal. Pneumatic air cylinders and 4-ways valves commonly use Buna-N rubber seals that are coated in mineral grease. [20]

Semi-synthetic oil

Semi-synthetic oils (also called "synthetic blends") are a mixture of mineral oil and synthetic oil, which are engineered to have many of the benefits of full synthetic oil without the cost. Motul introduced the first semi-synthetic motor oil in 1966. [21]

Lubricants that have synthetic base stocks even lower than 30% but with high-performance additives consisting of esters can also be considered synthetic lubricants. In general, the ratio of the synthetic base stock is used to define commodity codes among the customs declarations for tax purposes.

Other base stocks help semi-synthetic lubricants

API Group II- and API Group III-type base stocks help to formulate more economic-type semi-synthetic lubricants. API Group I-, II-, II+-, and III-type mineral-base oil stocks are widely used in combination with additive packages, performance packages, and ester and/or API Group IV poly-alpha-olefins in order to formulate semi-synthetic-based lubricants. API Group III base oils are sometimes considered fully synthetic, but they are still classified as highest-top-level mineral-base stocks. A synthetic or synthesized material is one that is produced by combining or building individual units into a unified entity. Synthetic base stocks as described above are man-made and tailored to have a controlled molecular structure with predictable properties, unlike mineral base oils, which are complex mixtures of naturally occurring hydrocarbons and paraffins. [22] [23]

Performance of synthetic oil

The advantages of using synthetic motor oils include better low-and high-temperature viscosity performance at service temperature extremes, [24] better (higher) Viscosity Index (VI), [25] and chemical and shear stability. [26] This also helps in decreasing the loss due to evaporation. [25] [27] [28] [29] It is resistant to oxidation, thermal breakdown, oil sludge problems [30] and provides extended drain intervals, with the environmental benefit of less used oil waste generated. It provides better lubrication in extreme cold conditions. [25] The use of synthetic oils promises a longer engine life [25] with superior protection against "ash" and other deposit formation in engine hot spots (in particular in turbochargers and superchargers) for less oil burn-off and reduced chances of damaging oil passageway clogging. [24] The performance of automobiles is improved as net increase in horsepower and torque due to less internal drag on engine. [30] Moreover, it can improve fuel efficiency - 1.8% to 5% as has been documented in fleet tests. [25]

However, synthetic motor oils are substantially more expensive (per volume) than mineral oils [31] and have potential decomposition problems in certain chemical environments (predominantly in industrial use). [32]

See also

Related Research Articles

A lubricant is a substance that helps to reduce friction between surfaces in mutual contact, which ultimately reduces the heat generated when the surfaces move. It may also have the function of transmitting forces, transporting foreign particles, or heating or cooling the surfaces. The property of reducing friction is known as lubricity.

<span class="mw-page-title-main">Petrochemical</span> Chemical product derived from petroleum

Petrochemicals are the chemical products obtained from petroleum by refining. Some chemical compounds made from petroleum are also obtained from other fossil fuels, such as coal or natural gas, or renewable sources such as maize, palm fruit or sugar cane.

<span class="mw-page-title-main">Ethylene glycol</span> Organic compound ethane-1,2-diol

Ethylene glycol is an organic compound with the formula (CH2OH)2. It is mainly used for two purposes, as a raw material in the manufacture of polyester fibers and for antifreeze formulations. It is an odorless, colorless, flammable, viscous liquid. It has a sweet taste, but is toxic in high concentrations. This molecule has been observed in outer space.

<span class="mw-page-title-main">Motor oil</span> Lubricant used for lubrication of internal combustion engines

Motor oil, engine oil, or engine lubricant is any one of various substances used for the lubrication of internal combustion engines. They typically consist of base oils enhanced with various additives, particularly antiwear additives, detergents, dispersants, and, for multi-grade oils, viscosity index improvers. The main function of motor oil is to reduce friction and wear on moving parts and to clean the engine from sludge and varnish (detergents). It also neutralizes acids that originate from fuel and from oxidation of the lubricant (detergents), improves the sealing of piston rings, and cools the engine by carrying heat away from moving parts.

<span class="mw-page-title-main">Hydraulic fluid</span> Medium to transfer power in hydraulic machinery

A hydraulic fluid or hydraulic liquid is the medium by which power is transferred in hydraulic machinery. Common hydraulic fluids are based on mineral oil or water. Examples of equipment that might use hydraulic fluids are excavators and backhoes, hydraulic brakes, power steering systems, automatic transmissions, garbage trucks, aircraft flight control systems, lifts, and industrial machinery.

An antifreeze is an additive which lowers the freezing point of a water-based liquid. An antifreeze mixture is used to achieve freezing-point depression for cold environments. Common antifreezes also increase the boiling point of the liquid, allowing higher coolant temperature. However, all common antifreeze additives also have lower heat capacities than water, and do reduce water's ability to act as a coolant when added to it.

<span class="mw-page-title-main">Gear oil</span> Lubricant used in vehicles and machinery

Gear oil is a lubricant made specifically for transmissions, transfer cases, and differentials in automobiles, trucks, and other machinery. It has high viscosity and usually contains organosulfur compounds. Some modern automatic transaxles do not use a heavy oil at all but lubricate with the lower viscosity hydraulic fluid, which is available at pressure within the automatic transmission. Gear oils account for about 20% of the lubricant market.

A coolant is a substance, typically liquid, that is used to reduce or regulate the temperature of a system. An ideal coolant has high thermal capacity, low viscosity, is low-cost, non-toxic, chemically inert and neither causes nor promotes corrosion of the cooling system. Some applications also require the coolant to be an electrical insulator.

A polyolefin is a type of polymer with the general formula (CH2CHR)n where R is an alkyl group. They are usually derived from a small set of simple olefins (alkenes). Dominant in a commercial sense are polyethylene and polypropylene. More specialized polyolefins include polyisobutylene and polymethylpentene. They are all colorless or white oils or solids. Many copolymers are known, such as polybutene, which derives from a mixture of different butene isomers. The name of each polyolefin indicates the olefin from which it is prepared; for example, polyethylene is derived from ethylene, and polymethylpentene is derived from 4-methyl-1-pentene. Polyolefins are not olefins themselves because the double bond of each olefin monomer is opened in order to form the polymer. Monomers having more than one double bond such as butadiene and isoprene yield polymers that contain double bonds (polybutadiene and polyisoprene) and are usually not considered polyolefins. Polyolefins are the foundations of many chemical industries.

<span class="mw-page-title-main">Zinc dithiophosphate</span> Lubricant additive

Zinc dialkyldithiophosphates are a family of coordination compounds developed in the 1940s that feature zinc bound to the anion of a dialkyldithiophosphoric salt. These uncharged compounds are not salts. They are soluble in nonpolar solvents, and the longer-chain derivatives easily dissolve in mineral and synthetic oils used as lubricants. They come under CAS number 68649-42-3. In aftermarket oil additives, the percentage of ZDDP ranges approximately between 2 and 15%. Zinc dithiophosphates have many names, including ZDDP, ZnDTP, and ZDP.

<span class="mw-page-title-main">Valve oil</span> Lubricant for brass instrument valves

Valve oil is a lubricant for valves of brass instruments. It is typically mostly mineral oil with a small amount of other ingredients, although synthetic oils are increasingly available.

<span class="mw-page-title-main">Rotary-screw compressor</span> Gas compressor using a rotary positive-displacement mechanism

A rotary-screw compressor is a type of gas compressor, such as an air compressor, that uses a rotary-type positive-displacement mechanism. These compressors are common in industrial applications and replace more traditional piston compressors where larger volumes of compressed gas are needed, e.g. for large refrigeration cycles such as chillers, or for compressed air systems to operate air-driven tools such as jackhammers and impact wrenches. For smaller rotor sizes the inherent leakage in the rotors becomes much more significant, leading to this type of mechanism being less suitable for smaller compressors than piston compressors.

<span class="mw-page-title-main">Polyolester</span> Family of synthetic refrigeration lubricants

Polyolester oil is a type of wax-free synthetic oils used in refrigeration compressors that is compatible with the refrigerants R-134a, R-410A, and R-12. POE oils are used as a lubricant in systems using the refrigerant HFC-134a when replacing CFC-12, as these systems traditionally use mineral oil, which HFC-134a does not mix well with. These oils are used with chlorine-free hydrofluorocarbon (HFC) refrigeration systems, as they provide better lubrication and stability and are more miscible with HFC refrigerants compared to synthetic and mineral oils of similar application. The dispersion behavior of POE oils has been studied for applications in nanotechnology.

<span class="mw-page-title-main">Shell Rotella</span> Brand of heavy-duty engine lubricant

Shell Rotella is a line of heavy-duty engine lubrication products produced by Shell plc. The line includes engine oils, gear oils and coolants. The oil carries both the American Petroleum Institute (API) diesel "C" rating as well as the API gasoline engine "S" rating. Ratings differ based on the oil. Rotella oils, like the T3 15W-40, meet both the API CJ-4 and SM specifications, and may be used in both gasoline and diesel engines. However, it is formulated specifically for vehicles without catalytic converters, containing phosphorus levels beyond the 600–800 ppm range. Therefore, Rotella is not recommended for gasoline vehicles with catalytic converters due to the higher risk of damaging these emission controls. Newer formulations of Rotella T6 however are API SM rated as safe for pre-2011 gasoline vehicles.

Oil additives are chemical compounds that improve the lubricant performance of base oil. The manufacturer of many different oils can utilize the same base stock for each formulation and can choose different additives for each specific application. Additives comprise up to 5% by weight of some oils.

Crude oil is extracted from the bedrock before being processed in several stages, removing natural contaminants and undesirable hydrocarbons. This separation process produces mineral oil, which can in turn be denoted as paraffinic, naphthenic or aromatic. The differences between these different types of oils are not clear-cut, but mainly depend on the predominant hydrocarbon types in the oil. Paraffinic oil, for example, contains primarily higher alkanes, whereas naphthenic oils have a high share of cyclic alkanes in the mixture.

<span class="mw-page-title-main">Automotive oil recycling</span> The process of recycling used engine and motor oils

Automotive oil recycling involves the recycling of used oils and the creation of new products from the recycled oils, and includes the recycling of motor oil and hydraulic oil. Oil recycling also benefits the environment: increased opportunities for consumers to recycle oil lessens the likelihood of used oil being dumped on lands and in waterways. For example, one gallon of motor oil dumped into waterways has the potential to pollute one million gallons of water.

Base oils are used to manufacture products including lubricating greases, motor oil and metal processing fluids. Different products require different compositions and properties in the oil. One of the most important factors is the liquid’s viscosity at various temperatures. Whether or not a crude oil is suitable to be made into a base oil is determined by the concentration of base oil molecules as well as how easily these can be extracted.

Pour point depressants are used to allow the use of petroleum based mineral oils at lower temperatures. The lowest temperature at which a fuel or oil will pour is called a pour point. Wax crystals, which form at lower temperatures, may interfere with lubrication of mechanical equipment. High-quality pour point depressants can lower a pour point of an oil additive by as much as 40°C.

Alkylated naphthalenes are chemical compounds made by the alkylation of naphthalene or its derivatives with an olefin. These compounds are used as synthetic base oils, and are claimed to have improved oxidative stability over some conventional base oils. Having an aromatic core, alkylated naphthalenes are better at solvating polar compounds than alkane mineral oils and polyalphaolefins.

References

  1. ↑ "How Synthetic Oil is Made". napaonline.com. 2016-11-28.
  2. ↑ Machinery Lubrication. "Conventional vs Synthetic Oil". Archived from the original on 2010-04-06. Retrieved 2017-03-24.
  3. ↑ "Synthetic oil: Is it right for your plane?". General Aviation News. 2005-03-11. Retrieved 2017-03-24.
  4. ↑ "Metal Stamping FAQs". Keats Manufacturing Co. Retrieved 2017-03-24.
  5. ↑ "Polyalphaolefin (PAO) Lubricants Explained". www.machinerylubrication.com. Retrieved 2022-06-26.
  6. 1 2 SynLube Incorporated. All About Synthetic Oil
  7. 1 2 3 Polyalkylene Glycol Synthetic PAG Oil Explained | Daryl Beatty, Dow Chemical Company and Martin Greaves, Dow Chemical Company
  8. ↑ Klueber | White Paper Polyglycol-based Oils
  9. 1 2 Croda Lubricants | Polyalkylene glycol base oils
  10. ↑ Understanding Polyalkylene glycol | Wil Escobar | Tribiology and Lubrication Technology | May 2008
  11. ↑ United States Environmental Protection Agency | Environmentally Acceptable Lubricants | 2.3 POLYALKYLENE GLYCOLS (page 5)
  12. ↑ EPA | Data Licensing Information for the U.S. Environmental Protection Agency | Unless otherwise specified, all data produced by the U.S EPA is by default in the public domain and is not subject to domestic copyright protection under 17 U.S.C. § 105.
  13. ↑ Klueber | White Paper Polyglycol-based Oils
  14. ↑ EPA Environmentally Acceptable Lubricants
  15. ↑ The Benefits of Switching to Synthetic Motor Oil
  16. ↑ United States Environmental Protection Agency | Environmentally Acceptable Lubricants | 3.4 ADVANTAGES AND DISADVANTAGES OF POLYALKYLENE GLYCOL-BASED EALS (page 8)
  17. ↑ Consumers Report Should You Use Synthetic Oil in Your Car?
  18. ↑ Mobil Glygoyle Series | Polyalkylene Glycol (PAG) Gear, Bearing and Compressor Lubricant
  19. ↑ New Equipment Digest | Benefits of Using PAG (Polyalkylene Glycol) Based Lubricants
  20. ↑ Modern Machinery | Polyalkylene Glycol Synthetic PAG Oil Explained
  21. ↑ DELPHI history
  22. ↑ ASTM Fuels & Lubricants Handbook, Hydrocarbon Chemistry, pg 169-184, section 7
  23. ↑ Wills, J. George (of Mobil Oil Corporation) (1980). Lubrication Fundamentals. M. Dekker. ISBN   9780824769765.
  24. 1 2 "Synthetic oil vs. conventional oil | Mobil Motor Oils". mobiloil.com. Retrieved 2017-03-24.
  25. 1 2 3 4 5 "Synthetic Motor Oil - GM High Tech Performance Magazine". Super Chevy. 2002-01-01. Retrieved 2017-03-24.
  26. ↑ Markova, L. V.; Makarenko, V. M.; Kong, H.; Han, H. -G. (2014). "Influence of viscosity modifiers on the rheological properties of synthetic oils". Journal of Friction and Wear. 35 (5): 351–358. doi:10.3103/S1068366614050092. S2CID   110320631.
  27. ↑ Synthetic verus Mineral Fluids in Lubrication | A. Jackson | Mobil Research and Development Corporation | December 1987 | Page 7 Figure 5. Comparison of the volatility (ASTM D1160) of polydecene and mineral-based SAE 10W-30 oils.
  28. ↑ Development and Application of a Lubricant Composition Model to Study Effects of Oil Transport, Vaporization, Fuel Dilution, and Soot Contamination on Lubricant Rheology and Engine Friction by Grace Xiang Gu B.S., Mechanical Engineering University of Michigan, 2012 | Page 96 … due to high temperatures near the top dead center of the piston, light volatile hydrocarbons vaporize and leave the system. Light carbon number species disappear at a faster rate due to their high volatility and vaporization rates. | Page 64 Figure 5-4: Viscosity curve for two different grades of oil using the Walther's formula | Page 68 Figure 5-5: Oil species boiling point and molecular weight.
  29. ↑ Oilap
  30. 1 2 "Why Use Premium Synthetic Motor Oil? Premium Synthetic Oil vs. Standard Oil". Royal Purple. Retrieved 2017-03-24.
  31. ↑ "Synthetic Vs. Mineral Motor Oil". Hot Rod Network. 2002-08-01. Retrieved 2017-03-24.
  32. ↑ "The Disadvantages of Using Synthetic Motor Oil". It Still Runs. Retrieved 2019-07-02.
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