Synthetic oil is a lubricant consisting of chemical
compounds that are artificially made. 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.
Synthetic oil is used as a
substitute for petroleum-refined oils when operating in extreme temperature.
Aircraft jet engines, for example, require the use of synthetic oils, whereas
aircraft piston engines do not. Synthetic oils are also used in metal stamping
to provide environmental and other benefits when compared to conventional
petroleum and animal-fat based products. These products are also referred to as
"non-oil" or "oil free".
Types of Synthetic Oil
Full
Some "synthetic" oil is
made from Group III base stock, some from Group IV. Some from 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 API [American Petroleum Institute] 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 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 some
synthetic lubricants. 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.
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 usually excellent lubricity are used for
various reasons as either "additives" or "base stocks" for
lubricants.
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.
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 of 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 entry.
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.
Performance
The advantages of using synthetic
motor oils include:
- Better low- and high-temperature viscosity
performance at service temperature extremes
- Better (higher) Viscosity Index (VI)
- Better chemical and shear stability
- Decreased evaporative loss
- Resistance to oxidation, thermal breakdown,
and oil sludge problems
- Extended drain intervals, with the
environmental benefit of less used oil waste generated
- Better lubrication during extreme cold
weather starts
- Possibly a longer engine life
- Superior protection against "ash"
and other deposit formation in engine hot spots (in particular in
turbochargers and superchargers) for less oil burnoff and reduced chances
of damaging oil passageway clogging.
- Net increase in horsepower and torque due to
less internal drag on engine
- Improved fuel efficiency - from 1.8% to up to
5% has been documented in fleet tests
- Research based study demonstrated that
synthetics performed about 47% better than regular oil
However, synthetic motor oils are
substantially more expensive (per volume) than mineral oils and have potential
decomposition problems in certain chemical environments (predominantly in
industrial use).
Oil needs to be changed because
it gets contaminated with combustion by-products that accumulate at about the
same rate regardless of oil type. Some vehicles require synthetic; therefore,
check your vehicle's owner manual to see what is recommended.
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