VISCOSITY AND THERMAL PROPERTIES OF TWO BRANDS OF
MOTOR OIL
A RESEARCH PROJECT
DEPARTMENT OF PHYSICS
ELECTRONICS AND COMPUTER TECHNOLOGY UNIT
FACULTY OF SCIENCE
UNIVERSITY OF CALABAR,
PMB 1115, CALABAR, NIGERIA.
IN PARTIAL FULFILLMENT OF THE REQUIREMENT FOR THE
AWARD OF BACHELOR OF SCIENCE (B.SC.) DEGREE IN ELECTRONICS AND COMPUTER
TECHNOLOGY
MAY, 2014
ABSTRACT
The viscosity and thermal properties
of two brands of motor oil, involves the measurement and analysis of oando
motor oil and pennzoil motor oil. This is done using dynamic viscosity test
which measures how viscous or how fluid an oil is and also kinematic viscosity test
which measures the density and calorimeter for thermal properties.
TABLE OF CONTENTS
Title page - - - - - - - i
Certification - - - - - - - ii
Dedication - - - - - - - iii
Acknowledgement - - - - - - iv
Abstract - - - - - - - - vi
Table of contents - - - - - - vii
CHAPTER
ONE
1.1 Introduction - - - - - - 1
1.2 Basic Principle of Lubrication - - - 3
1.3 Thermal Degradation - - - - 7
1.4 Corrosion - - - - - - 8
1.5 Shearing - - - - - - - 10
1.6 Contamination - - - - - 12
CHAPTER
TWO
2.1 Viscosity of Oil - - - - - 15
2.1.1 Viscosity Index Improver - - - 18
2.1.2 Viscosity Grades - - - - - 21
2.3 Motor Oil SAE Viscosity Classification - 26
CHAPTER
THREE
3.1 Motor Oil - - - - - - - 29
3.2 Types of Motor Oil - - - - - 30
3.3 Motor Oil Refining Process - - - 32
3.4 Complex Blended Oil Additive - - - 35
CHAPTER
FOUR
4.1 Motor Oil Viscosity Testing - - - 37
4.2 Concerting to Synthetic Motor Oil - - 45
CHAPTER
FIVE
5.1 Summary - - - - - - 48
5.2 Conclusion - - - - - - 48
References - - - - - - 50
CHAPTER ONE
1.1 Introduction
One
of the largest applications for lubricant, in the form of motor oil, is
protecting internal combustion engines. Using the correct motor oil with its
appropriate viscosity and thermal properties helps motor engines run smoothly.
Primarily, oil stops the metal surfaces in engines from grinding together and
wearing by creating a separating oil film between them.
The
oil also disperses heat and reduces wear thereby protecting the engine. On top
of this, good oil with adequate viscosity and thermal properties prevents dirt
build up and deposits by keeping them in suspension. Motor oil even protects
against sludge and fights oxidation, keeping the oil fresh and minimizing acids
which can cause corrosion in a short time.
Viscosity is a measure of a
“flowability” of an oil. Specifically it is the property of an oil to develop
and maintain a certain amount of sheering stress dependent on flow and then to
offer continuous flow. (Hackett, 1999). Thicker oil generally have higher viscosity,
and thinner oils a lower viscosity; this is the most important property for
motor engine oils. An oil with too low viscosity can shear and loose film
strength at high temperatures while an oil with too high a viscosity may not
pump to the proper parts at low temperatures and film may tear at high
temperature.
The
weight given amount are arbitrary numbers assigned by the society of automotive
engineers (S.A.E). These numbers correspond to “real” viscosity as measured by
several accepted techniques and these measurement are taken at specific
temperatures.
Typically, motor viscosity and their
thermal properties are interesting in terms of how they influence the return of
the lubricant to the compressor.
Furthermore,
when hearing the word “viscosity” the thicker a liquid, the higher the
viscosity why the lower the viscosity the thinner the liquid. While the
definition also applies to oil, the system uses labels. The viscosity of
Passanger Car Oil (PCEO) is one of the least understood automotive specifications.
The lower the heat transfer fluids viscosity, the less the energy that would be
required to pump it through the system.
1.2 Basic Principle of Lubricant
Before a proper lubricant is
selected for a specific application some basic theory must be understood. When
one surface moves over another there is always some degree of resistance to
movement called friction. Friction can manifest it self in varying degrees from
smooth easy sliding to uneven erratic movement, which can generate excessive heat
and cause damage to moving surfaces.
Friction is good when it causes the
brakes and tries on cars and tracks to stop the vehicle or when it keeps our
shoes from slipping on wet surfaces, yet friction is bad when it causes heat,
wears and reduces energy in an engine or gearbox.
Lubrication is simply the use of a
material to improve the smoothness of movement by reducing friction. The
immediate result is reduced wear and reduced heat generation. There are
numerous types of lubricants but for this project the main consideration is
synthetic and petroleum motor oils.
The
needed force to start the movement is defined as static friction and is
typically always greater that the dynamic friction, which is the force required
to keep the two materials moving at the same speed once initial movement has
started, Dave (2008). Different oils and different materials loading condition
can create vastly different coefficients of friction that can affect
performance and longevity of an engine and other mechanical components.
A
few basic key functions of a motor oil is to reduce friction under all extremes
of operating condition, prevent corrosion of internal engine components and
provide cooling via transfer of heat.
When it comes to reduction of
friction (as well as preventing corrosion and providing effective heat
transfer), for example when using a petroleum oil, under certain conditions,
the lubricant film can be either too thin, thus allowing metal-to-metal contact
or too viscous which causes high internal friction within the layers of the
oil. The key is to select an oil grade that is thin enough to have low internal
friction coefficient, yet still high enough to effectively separate two metal
surfaces under all operational conditions and prevent excessive wear and heat
generation.
The
fact proves that synthetic oil because of its good film allows the oil to flow
freely for low internal friction, yet still effectively separate metal-to-metal
contact surfaces under normal and extreme operating condition and significantly
reduce internal wear.
When
looking at metal surfaces, such as piston to cylinder, and it is visually seen
that they appear smooth, this does not accurately reflect reality until when
viewed under a high powered microscope. The smoothest machined surfaces are
rough and are viewed as million of peaks and valleys.
These
peaks are under extremely high loading and need to wear in (commonly called
break-in) on a new engine.
However,
there is much discrepancy among automotive and motorsports enthusiast as to how
the length of time required for engine wear-in and whether or not petroleum oil
must be used for the initial wear-in. (Oscar, 1950).
1.3 Thermal Degradation
Whenever a motor oil is heated
beyond a certain temperature, it will start to degrade, even if there is no
oxygen present. This is called thermal degradation and causes the oil to change
viscosity. (Marthin, 2004). The thermal stability of a motor oil cannot be
improved by use of additives but it can be improved by refining out the same
compounds that decrease the oxidation resistance. As temperature increases,
thermal degradation increases. In order for oil to provide proper service protection
at high operating temperature, highly refined oils with plenty of anti-oxidant
should be used. There is also a direct correlation between price of a
particular oil and it’s performance under temperature extremes, less costly
oils are generally refined less and have a lower capability to prevent/reduce
thermal degradation.
Petroleum
oil has a lower thermal property operating temperature range while premium
quality synthetic motor oil brands have a very high operating temperature range
and are much more resistant to thermal degradation.
1.4 Corrosion
Petroleum oil that is new or kept
clean by proper filtration is generally non-corrosive and will provide good
protection against corrosion caused by the atmosphere. However, inside an
engine oil oxidation by-products will attack internal engine steel and bearing
materials that are typically manufactured aluminum, copper, lead and tin (a Lead
Tin Flashing is used for break-in purpose on the few engines that use aluminum
rod and main bearing). Most gasoline and diesel engines use copper lead main
and connecting rod bearings.
The water present due to condensation
caused by temperature and humidity changes or short stop and driving where the
engine never reaches the proper operating temperature, although still hotter
then the ambient temperature, can also cause corrosion. The hotter the oil when
water is present, the more the chemical reaction is and corrosion related
damage could definitely occur. In addition, water present in an oil for an
extended period of time can emulsify the oil and form a mixture which is much
more corrosive than the two components alone and can then form a sluge which
may block oil filter or small passages. It is critical to operate an engine at
normal operating temperature to prevent as well as burn off any water that is
present by an evaporation process. The most severe type of driving an oil can be
subjected to (as well as an internal components) is short drives and
intermittent operation in which the engine and oil never have time to reach
normal operating temperatures for an extended period of time.
A
quality motor oil will have a corrosion inhibitor added. Corrosion inhibitors
also vary in terms of effectiveness, quality and quantity.
1.5 Shearing
The word “oil breaking”, is used by
many people to represent what they think is a motor oil that is “broken down”
and is in need of changing, when in reality the actual process of “break down”
is not properly understood. The correct word for this is oil break down due to
shear forces. An internal combustion engine imparts high shear forces on a
motor oil, which is mixed between two rotating sliding forces under load and
heat. The molecular structure is essentially torn apart by these mechanical shear
forces. The component of the oil affected most by these shear forces is the
viscosity improver.
These
viscosity improvers allow the manufacturer of the oil to create multi-grade
oils suitable for a wider temperature range of operation. The end result of
these shear forces is a decrease in the viscosity of the oil as well as a
decrease in the viscosity index. Once a motor oil has sheared beyond a specific
point it will not revert back to it is base structure when it cools down and
the shear forces have ceased. This
does not affect synthetic oil because synthetic motor oils are extremely
resistant to the detrimental effects of shear forces.
This phenomenon can be explained
thus: A look at the molecular structure of motor oil under a microscope we see
chains of molecules grouped together and linked together. The smaller molecular
particles are attached to the larger ones. As an oil shears these smaller
molecules break away and align in the chain. As engine heat and shear forces
continue and increase these molecules break away from the base structure and in
the process provide less and less resistance to wear. If this shearing
continues over an extended period of time engine damage can occur. If shearing
is not much then when the oil cools down the structure will be never back to
its original structure and still be capable of providing proper engine
protection. (Khomenko, 2007).
1.6 Contamination
Contamination of motor oil causes
deterioration of the oil. Some of the more common contaminant sources include
dirt, sand and dust from the air, soot, unburned fuel in the oil, water from
condensation of the combustion process, wear, metal particulates that oil
filter cannot trap and hold, corrosion by-products and additive elements that
have degraded. A combination of dirt, sand and dust can continue to enter the
engine and, in addition to creating more wear, combine with other contaminants
and cause more damage than they would separately.
One of the many by-products of
combustion is soot. Soot can be highly
abrasive as well as cause filters to become filled and/or plugged in extreme
cases. Another contaminant is acidic by-product of combustion, which can
produce highly corrosive mixture and cause corrosion and pitting of internal
engine component and additional generation of wear debris. These same acidic
solutions can also mix with water inside the engine and form an emulsion that
can cause problems with oil filters and passageways.
Yet another source of contamination
is fuel. A charge of fuel is rarely 100% burned during the combustion process.
This unburned fuel can mix with the oil present in the cylinders.
Fuel
contamination can also be caused by worn sealing components such as excessive
piston ring to cylinder clearances allowing unburned fuel to blow-by the rings.
When a motor oil is diluted with fuel the effect is that the viscosity is
lowered. If this reaches extremes of contamination excessive wear and engine
damage can take place. Operating an engine not sufficiently warned up can also
increase combustion, blow-by. It is much better to let your engine sufficiently
warm up before driving away which can have a significant effect on preventing
fuel blow by as well as producing a much more efficient combustion cycle.
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