This document discusses lubricating oils used in mechanical engineering. It begins by defining lubricating oils and their uses in reducing friction and wear between surfaces. It then discusses the key properties oils should have and different types including mineral oils derived from petroleum and vegetable/animal oils. The rest of the document discusses additives used in mineral oils, classification systems for oils, and commercial automotive lubricants and their properties.

1. DEPARTMENT OF MECHANICAL
ENGINEERING
3210 DHARMESH KAHIRE
3212 SHUBHAM KHATAL
3204 SAGAR KALE
3205 SANKET KALE
3206 VAIBHAV KARLE
AMRUTVAHINI COLLEGE OF
ENGINEERING
NEAR PUNE NASHIK HIGHWAY, AHMEDNAGAR, SANGAMNER, MAHARASHTRA
422608

2. o Lubricating oils are a type of oil that are used to
reduce friction and wear between two surfaces in
contact with each other.
o These oils are used in a variety of machinery,
including engines, gearboxes, and hydraulic
systems

3. (i) It should be available in a wide range of viscosities.
(ii) (ii) There should be little change in viscosity of the oil with change
in temperature.
(iii)(iii) The oil should be chemically stable with the bearing material
and atmosphere at all temperatures encountered in the application
(iv) The oil should have sufficient specific heat to carry away frictional
heat, without abnormal rise in temperature.
(v) It should be commercially available at reasonable cost.

4. Mineral oils
Vegetable or Animal
oils

5.  Mineral oils are a class of oils derived from petroleum or crude oil,
which is a complex mixture of hydrocarbons.
 These oils have been used for a variety of purposes, such as
lubrication, fuel, and as a source of chemicals for many industrial
processes.
 Mineral oils have been used for thousands of years, with evidence
of their use dating back to ancient civilizations such as the Greeks
and Romans

6. Mineral oils consist of hydrocarbons, which are obtained by the
distillation of crude oil.
 There are two different classes of mineral oils—those with a
paraffinic series and those with a naphthenic series.
 A paraffinic oil is composed of straight and branched chains of
hydrocarbons defined by the general formula CnH(2n + 2).
 A naphthenic oil is composed of a saturated single-ring
formation of hydrocarbons defi ned by the general formula
CnH2n.

8. The Society of Automotive Engineers (SAE) of USA has
classified lubricating oils by a number, which is related to
the viscosity of the oil in Saybolt Universal Seconds.
 This classification is based on only one property of
lubricating oils, namely, viscosity.
According to this system, automotive oils are classified in
accordance with Table 16.5
It can be observed from this table that the SAE number
corresponds to approximately one-half of the viscosity of
oil at 210°F measured in terms of SUS.
When the SAE number is more, it indicates more viscous
oil. The viscosities in the above table are measured at only
one fixed temperature, i.e. 210°F.
 It does not indicate the full picture of the viscosity–
temperature relationship. It is, therefore, necessary to
specify viscosities of these oils at a low temperature.

9. This is achieved by specifying viscosities at 0°F as shown in the
following table:
The letter W in the above table indicates winter grading of oils.

10. Vegetable and animal oils are a class of oils that are derived from
plant and animal sources, respectively. These oils have been used for a
variety of purposes, such as food, fuel, and as a source of chemicals for
many industrial processes.
The use of vegetable and animal oils dates back thousands of years,
with evidence of their use in ancient civilizations such as the
Egyptians and Greeks.

11.  Vegetable oils used for lubrication are castor oil, rapeseed oil, palm oil
and olive oil.
 Lubricating oils of animal origin are lard oil, tallow oil and certain oils
obtained from marine species, such as whales, sperms or dolphin jaws.
 They are biodegradable and have low toxicity, which makes them a good
choice for environmentally sensitive applications.
 However, vegetable oils typically have lower oxidation stability than
mineral or synthetic oils, which means they can break down more easily
over time and form deposits.

12. (i) Mineral oils are chemically inert.
(ii) They have a wide range of viscosities, corresponding to different
values of n in the general formula.
(iii) They have little tendency to oxidise or form corrosive acids.
(iv) After periodic fi ltration, they can be reused without any loss or
change of their properties.
(v) At normal temperature, they are not liable to spontaneous ignition

13. (i) These oils are sometimes referred to as fixed oils because they are non-
volatile, unless there is chemical decomposition. This property prevents
them from being expelled from intimate contacts of solid surfaces by
frictional heat.
(ii) They retain their viscosities at high temperature much better than
mineral oils.
(iii) These oils are called ‘polar’ compounds. They have a long chain of
molecules with positive and negative charges at the two ends. One end of
the polar molecule adheres to the surface of the journal or bearing and the
long chain of molecules extends into clearance space. They form ‘clusters’
which prevents metal to metal contact in boundary lubrication

14. (i) At low temperature, these oils solidify and become ‘fats’. The fat is
melted at about 65°C and becomes oil.
(ii) These oils react with oxygen in the atmosphere and become acidic.
In some cases they change from the liquid state to an elastic solid
form. Due to this reason, they are termed ‘drying oils’.
(iii)They are subjected to saponifi cation either by contact with base
metals or with hot water. They produce glycerol and some organic
acids, which attack metallic surfaces and form metallic soaps.

15. 1) Castor oil was used in the past as a lubricant in racing
cars and aero-engines.
2) Rapeseed oil is added to mineral oil to increase viscosity.
Cottonseed oil is mainly used as a thickener in mineral
oils.
3) Lard oil is used as cutting oil, while tallow oil is used as
cylinder oil.
4) In light machine tools, sperm oil is used for spindle

16.  Mineral oil additives are chemical compounds that are added to
mineral oils to improve their performance and properties.
 Mineral oils are derived from petroleum or crude oil, and are
widely used in various applications such as lubrication, hydraulic
fluids, and heat transfer fluids.
 However, mineral oils have certain limitations in terms of their
properties, such as low viscosity index, poor thermal stability, and
low resistance to oxidation and corrosion.

17. Detergents
Dispersants
Anti-wear agents
Extreme pressure agents
Viscosity index improvers
Pour point depressants
Antioxidants
Corrosion inhibitors

18. • Detergents are a type of additive that are commonly
used in mineral oils to improve their cleaning
properties.
• Detergents are organic compounds that have the
ability to dissolve and remove contaminants from
surfaces, including engine parts and other mechanical
components.

19. Dispersants are a type of additive that are commonly used in mineral
oils to improve their ability to disperse and suspend contaminants,
such as soot, dirt, and other particles.
Dispersants are organic compounds that have the ability to absorb
onto the surface of contaminants and prevent them from clumping
together and forming deposits.
There are two main types of dispersants used in mineral oils: ash-
containing dispersants and ashless dispersants.
Ash-containing dispersants contain metal compounds and are
typically used in older engine designs, while ashless dispersants do
not contain metal compounds and are commonly used in newer engine
designs.

20. Anti-wear agents are a type of additive that are
commonly used in mineral oils to reduce friction and
wear between moving parts in engines and other
mechanical components.
 Anti-wear agents are typically organic compounds
that form a protective layer on the surface of metal
parts, helping to prevent direct contact and reduce
friction and wear.
There are several types of anti-wear agents used in
mineral oils, including zinc dialkyldithiophosphate
(ZDDP), boron compounds, and molybdenum
compounds
 Each type of anti-wear agent has a specific function
and is designed to improve the performance of
mineral oils under different operating conditions

21.  Extreme pressure agents are a type of additive that are commonly used in
mineral oils to reduce friction and wear under high pressure and load
conditions.
 Extreme pressure agents are typically organic compounds that form a
protective layer on the surface of metal parts, helping to prevent direct
contact and reduce friction and wear even under extreme operating
conditions.
 There are several types of extreme pressure agents used in mineral oils,
including sulfur compounds, phosphorus compounds, and chlorine
compounds.
 Each type of extreme pressure agent has a specific function and is designed
to improve the performance of mineral oils under different high-pressure
and high-load operating conditions

22.  A viscosity index improver is a substance which when added to mineral oils,
increases viscosity at high temperatures.
 These additives are polymerized resins of high molecular weight, such as
polyisobutylene, polymethacrylate ester and polyfumarite ester.
 The popular VI improver is ‘paratone’ which is a polymer of butylene having
the formula (C4H8)n where n varies from 180 to 270.
 Due to the large size of the molecule, the additive has extremely high
viscosity. When added to the base oil, it increases viscosity at high
temperature.
 At low temperature, the molecules are coiled and remain as colloidal
suspension in the base oil. As the temperature increases, they uncoil, go into
solution and increase its viscosity.
 This improves the viscosity index of the base oil. Normally, 1 to 2 per cent
VI improver is added to the base oil.

23. Pour point is the lowest temperature at which the oil can flow.
This is an important characteristic when the lubricant is used in
refrigeration and air-conditioning equipment.
Mineral oils of paraffinic origin contain some amount of wax. When the
temperature decreases below the pour point, the wax is separated in the
form of needle shaped crystals.
 These crystals join with each other and form a matrix. The oil is held in the
matrix in much the same fashion as water is retained in sponge.
 The mineral oil, therefore, ceases to function as a fluid. ‘Paraflow’ is used as
a pour point depressant.
 This type of additive surrounds the wax crystals in the form of a coating
and prevents them from forming a large size matrix. The small-size crystals
remain in suspension, but do not affect the fl uidity of the base oil.

24. Antioxidants are a type of additive that are commonly used in mineral
oils to prevent or slow down the oxidative degradation of the oil.
Oxidative degradation occurs when the oil reacts with oxygen in the air,
resulting in the formation of sludge, deposits, and other harmful
byproducts that can reduce the performance of the oil and damage
engines and other mechanical components.
There are several types of antioxidants used in mineral oils, including
hindered phenols, amines, and phosphites.
Each type of antioxidant has a specific function and is designed to
improve the performance of mineral oils under different operating
conditions.

25. Corrosion inhibitors are a type of additive that are commonly used in
mineral oils to prevent or reduce the corrosion of metal parts in contact
with the oil.
 Corrosion can occur when the oil reacts with moisture, acids, or other
corrosive substances, leading to the formation of rust, scale, or other
harmful byproducts that can damage engines and other mechanical
components.
There are several types of corrosion inhibitors used in mineral oils,
including organic and inorganic compounds.
Each type of corrosion inhibitor has a specific function and is designed to
improve the performance of mineral oils under different operating
conditions.

26.  Lubricating oils are commercially available
under different trade names. Indian Oil
Corporation5 manufactures a wide range of
lubricating oils and greases.
 These commercial lubricants contain a base
oil and a group of additives, which are
suitable for a given application.
 The properties of lubricating oils used for
automotive applications are given in Table
16.6.

27. There are five grades from SAE 10 to SAE 50. These base oils are
blended with viscosity index improver, detergent additives and oxidation
inhibitors.
These oils are used for engine lubrication of petrol and diesel vehicles.
They are also used for generators and pumping sets operating on diesel
engines.
There are two different classes of crankcase oil—Servo Engine Oil and
Servo Super. The second is superior and costly. It is used for heavy duty
internal combustion engines
2T oil is a popular variety of lubricating oil used on two-stroke engines in
scooters, mopeds and motorcycles

28. (i) 2T oil, also known as two-stroke oil, is a type of lubricant that
is specifically designed for use in two-stroke engines.
(ii) Two-stroke engines are commonly used in small handheld
equipment such as chainsaws, leaf blowers, and motorcycles.
(iii)The composition of 2T oil is typically a blend of mineral or
synthetic base oils, combined with various additives such as
detergents, dispersants, and anti-wear agents.
(iv) The specific composition of 2T oil can vary depending on the
requirements of the engine manufacturer, as well as the
operating conditions in which the engine is used

29. (i) It is self-mixing with petrol.
(ii) It keeps the piston, piston rings, cylinder, plugs and
exhaust port clean.
(iii) It prevents corrosion of engine components.
(iv) It controls deposits in the combustion chamber and
reduces pre-ignition. It consists of SAE 30 as base oil, and
detergent additives. The recommended fuel/oil ratio varies
from 12:1 to 50:1 depending upon the engine.

31. Commercial lubricating oils for
gears consist of SAE 80, SAE 90
and SAE 140 as base oils and a
mixture of extreme-pressure
additives, oxidation inhibitors
and oiliness additives. The
properties of these oils are given
in Table 16.7