UNIVERSITI TEKNIKAL MALAYSIA MELAKA

THE STUDY OF EFFECT OF ENGINE OIL VISCOSITY ON

ENGINE PERFORMANCE

This report is submitted in accordance with the requirement of the Universiti

Teknikal Malaysia Melaka (UTeM) for the Bachelor of Mechanical Engineering

Technology

(Automotive Technology) with Honours

by

MUHAMMAD ARIF BIN KAMALRUZAMAN

B071210180

931212-01-6465

FACULTY OF ENGINEERING TECHNOLOGY

2015

UNIVERSITI TEKNIKAL MALAYSIA MELAKA

BORANG PENGESAHAN STATUS LAPORAN PROJEK SARJANA MUDA

TAJUK: The Study of Effect of Engine Oil Viscosity on Engine Performance

SESI PENGAJIAN: 2015/16 Semester 1

Saya MUHAMMAD ARIF BIN KAMALRUZAMAN

mengaku membenarkan Laporan PSM ini disimpan di Perpustakaan Universiti

Teknikal Malaysia Melaka (UTeM) dengan syarat-syarat kegunaan seperti berikut:

1. Laporan PSM adalah hak milik Universiti Teknikal Malaysia Melaka dan penulis. 2. Perpustakaan Universiti Teknikal Malaysia Melaka dibenarkan membuat salinan

untuk tujuan pengajian sahaja dengan izin penulis. 3. Perpustakaan dibenarkan membuat salinan laporan PSM ini sebagai bahan

pertukaran antara institusi pengajian tinggi.

4. **Sila tandakan ( )

SULIT

TERHAD

TIDAK TERHAD

(Mengandungi maklumat yang berdarjah keselamatan

atau kepentingan Malaysia sebagaimana yang termaktub

dalam AKTA RAHSIA RASMI 1972)

(Mengandungi maklumat TERHAD yang telah ditentukan

oleh organisasi/badan di mana penyelidikan dijalankan)

(TANDATANGAN PENULIS)

Alamat Tetap:

NO. 3, Jalan Universiti 14, Taman

Universiti

86400 Parit Raja,

Johor Darul Takzim

Tarikh: ________________________

Disahkan oleh:

(TANDATANGAN PENYELIA)

Cop Rasmi:

Tarikh: _______________________

** Jika Laporan PSM ini SULIT atau TERHAD, sila lampirkan surat daripada pihak berkuasa/organisasi

berkenaan dengan menyatakan sekali sebab dan tempoh laporan PSM ini perlu dikelaskan sebagai

SULIT atau TERHAD.

iii

DECLARATION

I hereby, declare that this report entitled “The Study of Effect of Engine Oil

Viscosity on Engine Performance” is the result of my own research except as cited in

the references.

Signature :………………………

Name : ………………………

Date : ………………………

iv

APPROVAL

This report is submitted to the Faculty of Engineering Technology of UTeM as a

partial fulfilment of the requirement for the Degree of Bachelor of Engineering

Technology Mechanical Engineering (Automotive Technology) (Hons.). The

member of the supervisor are as follows:

……………………………….

(En. Ahmad Zainal Taufik Bin Zainal Ariffin)

Supervisor

v

ABSTRACT

There are some regulations for specific engine on choosing the engine

oil. The manufacturers of car company have listed type and viscosity of

engine oil that can be used by the user to their engine. The manufacturer have

stated that certain viscosity and type of engine oil only suitable for their

engine to long lasting life of engine and give high performance to the engine.

In this study the characteristics and effects of viscosity to the engine

performance to justify the manufacturers claim will be studied. This study

focused on the effect of the engine oil to the engine performance. There are 3

types of engine oil that were being tested in this project, which are mineral

based oil, semi-synthetic oil, and fully synthetic oil. All these engine oil have

their own viscosity to differentiate between each other. The engine being

used for this test is 1.3 L Campro engine and the equipment used are Exhaust

Gas Analyzer and LAUNCH X431 Scanner Tool. The method chosen for this

project is that the engine oil must be run at different rpm, which is at 800

RPM for idle speed and 3000 RPM for top speed. The test will be justified

based on the gas emission release from the exhaust and relate it to the engine

performance. The data from the scanner tool also being analysed to relate

with the engine performance.

vi

ABSTRAK

Terdapat beberapa panduan untuk enjin tertentu dalam memilih minyak

enjin. Pengeluar syarikat kereta telah menyenaraikan jenis dan kelikatan minyak

enjin yang sesuai digunakan oleh pengguna untuk enjin mereka. Pengilang telah

menyatakan bahawa kelikatan tertentu dan jenis minyak enjin hanya sesuai untuk

enjin mereka untuk ketahanan enjin dan memberikan prestasi tinggi untuk enjin.

Dalam kajian ini, ciri-ciri dan kesan kelikatan dengan prestasi enjin untuk

mewajarkan tuntutan pengeluar akan dikaji. Kajian ini memberi tumpuan kepada

kesan minyak enjin kepada prestasi enjin. Terdapat 3 jenis minyak enjin yang diuji

dalam projek ini, iaitu minyak asas mineral, minyak semi-sintetik dan minyak

sintetik sepenuhnya. Semua minyak enjin ini mempunyai kelikatan tersendiri untuk

membezakan antara satu sama lain. Enjin yang digunakan untuk ujian ini ialah enjin

1.3 L Campro dan peralatan yang digunakan adalah Exhaust Gas Analyzer dan

LAUNCH X 431 Scanner Tool. Kaedah yang dipilih untuk projek ini adalah minyak

enjin mesti dijalankan pada rpm yang berbeza, iaitu pada 800 rpm untuk kelajuan

terbiar dan 3000 rpm untuk kelajuan tertinggi. Ujian ini dianalisa melalui pelepasan

gas dari ekzos dan mengaitkannya dengan prestasi enjin. Data daripada alat

pengimbas juga dianalisis untuk mencari perkaitan dengan prestasi enjin.

vii

DEDICATIONS

I dedicated this final year project report to my beloved father and mother, En.

Kamalruzaman Bin Atan & Puan Norzanita Binti Syed Sulaiman Sahib, and my

lovely family.

viii

ACKNOWLEDGMENTS

First of all, I express my deepest thanks and gratitude to Allah S.W.T who

has given me the spirit and the soul throughout the duration of my final year project.

I have completed this project even though there are many difficulties and hardship

along the way.

I would like to express my appreciation and deep respects to my supervisor,

Mr. Ahmad Zainal Taufik Bin Zainal Ariffin, for his constant guidance, and

encouragement and critical comment throughout this project. Not to forget, Datin

Fadzilah Binti Salim, my co-supervisor for her guidance and support during my

report writing.

My thanks go to all my lecturers who have taught me, directly or indirectly,

for all these four years. Also to all my friends, thank you for the help and friendship.

Lastly, thanks to my beloved father, mother, and my family, who have been

the loveliest advisor, giving me the constant support, love, care and inspiration

throughout my campus life.

To all mentioned the above, this final year project report will not be realized

without you.

ix

TABLE OF CONTENTS

DECLARATION ................................................................................................................. iii

APPROVAL ......................................................................................................................... iv

ABSTRACT ........................................................................................................................... v

ABSTRAK ........................................................................................................................... vi

DEDICATIONS .................................................................................................................. vii

ACKNOWLEDGMENTS ................................................................................................. viii

TABLE OF CONTENTS ..................................................................................................... ix

LIST OF FIGURES ........................................................................................................... xiii

LIST OF TABLE ............................................................................................................... xiv

LIST OF SYMBOLS AND ABBREVIATIONS ................................................................ xv

CHAPTER 1 .......................................................................................................................... 1

1.0 Background ............................................................................................................. 1

1.1 Problem Statement .................................................................................................. 2

1.2 Objectives ................................................................................................................ 2

1.3 Scope ....................................................................................................................... 3

1.3.1 Engine Oil ................................................................................................. 3

1.3.2 Engine ....................................................................................................... 3

1.3.3 Test Method .............................................................................................. 3

CHAPTER 2 .......................................................................................................................... 4

2.0 Introduction ............................................................................................................. 4

x

2.1 Lubricant ................................................................................................................. 4

2.2 Mineral oil ............................................................................................................... 5

2.3 Synthetic Oil ............................................................................................................ 6

2.4 Semi-synthetic oil .................................................................................................... 7

2.5 Viscosity .................................................................................................................. 8

2.6 Oil Standard ........................................................................................................... 11

2.7 Additive ................................................................................................................. 13

2.8 Engine &Performance ........................................................................................... 14

2.9 Exhaust emissions ................................................................................................. 15

2.9.1 Carbon monoxide (CO) emissions .......................................................... 15

2.9.2 Nitrogen oxides (NOx) emissions........................................................... 15

2.9.3 Carbon dioxide (CO2) emissions ............................................................ 16

2.9.4 Hydrocarbon (HC) emissions ................................................................. 17

CHAPTER 3 ........................................................................................................................ 18

3.0 Introduction ........................................................................................................... 18

3.1 Material Selection .................................................................................................. 19

3.1.1 Mineral Oil .............................................................................................. 19

3.1.2 Semi-Synthetic Oil .................................................................................. 20

3.1.3 Fully Synthetic Oil .................................................................................. 21

3.2 Sample Preparation ................................................................................................ 22

3.3 Engine Selection .................................................................................................... 22

3.4 Area of Test ........................................................................................................... 23

3.5 Sample Testing ...................................................................................................... 23

xi

3.5.1 Exhaust Gas Analyzer (Model 5002)...................................................... 23

3.5.2 Launch X431 GX3 Multi-language Diagnostic Tool ............................. 24

3.6 Experimental Procedure ........................................................................................ 25

3.6.1 Exhaust Gas Analyzer Test Procedure .................................................... 25

3.6.2 Using Launch X431 GX3 Multi-Language Diagnostic Tool procedure 27

3.7 Data Collection ...................................................................................................... 28

CHAPTER 4 ........................................................................................................................ 29

4.0 Introduction ........................................................................................................... 29

4.1 Experimental Data ................................................................................................. 29

4.2 Exhaust gas analyzer ............................................................................................. 30

4.2.1 Hydrocarbon (HC) .................................................................................. 31

4.2.2 Carbon Monoxide (CO) .......................................................................... 33

4.2.3 Carbon dioxide (CO2) ............................................................................ 35

4.2.4 Nitogen Oxide (NOx) ............................................................................. 37

4.2.5 Oxygen (O2) ........................................................................................... 39

4.2.6 Air Fuel Ratio (AFR) .............................................................................. 41

4.3 Launcher X431 Scanner Tool ................................................................................ 43

4.3.1 Engine Temperature ................................................................................ 43

4.3.2 Intake Air Temperature ........................................................................... 45

4.3.3 Manifold Pressure ................................................................................... 47

CHAPTER 5 ........................................................................................................................ 49

5.0 Introduction ........................................................................................................... 49

5.1 Conclusion ............................................................................................................. 49

xii

5.2 Recommendation for future research .................................................................... 54

REFERENCES ..................................................................................................................... 55

xiii

LIST OF FIGURES

Figure 2-1 : Example of viscosity range of various SAE grades (Rohr et al.,2013) .. 11

Figure 2-2 : Viscosity requirement for SAE grades (Rohr et al.,2013) ..................... 12

Figure 3-1 : Study Flow Chart ................................................................................... 18

Figure 3-2 : Petronas Mach 5 Specification ............................................................... 19

Figure 3-3 : Petronas Mach 5 ..................................................................................... 19

Figure 3-4 :Petronas Syntium 800.............................................................................. 20

Figure 3-5 : Petronas Syntium 800 Specification ...................................................... 20

Figure 3-6 : Petronas Syntium 3000.......................................................................... 21

Figure 3-7 : Petronas Syntium 3000 Specification .................................................... 21

Figure 3-8 :1.3 L Campro Engine .............................................................................. 22

Figure 3-9: Exhaust Gas Analyzer (Model 5002) ...................................................... 24

Figure 3-10 : Launch X431 GX3 Multi-language Diagnostic Tool ........................... 24

Figure 3-11: Draining of engine oil ........................................................................... 26

Figure 3-12 : Insert the probe .................................................................................... 26

Figure 3-13 : Example of data taken from Exhaust Gas Analyzer ............................ 27

Figure 3-14: Setting the diagram system ................................................................... 28

Figure 3-15 : Example of data taken from scanner tool ............................................. 28

Figure 4-1: HC versus RPM ....................................................................................... 32

Figure 4-2: CO vs RPM ............................................................................................. 34

Figure 4-3: CO2 vs RPM ........................................................................................... 36

Figure 4-4: NOx vs RPM ........................................................................................... 38

Figure 4-5: O2 vs RPM .............................................................................................. 40

Figure 4-6: AFR vs RPM ........................................................................................... 42

Figure 4-7: Engine temperature vs RPM ................................................................... 44

Figure 4-8: Intake air temperature vs RPM ............................................................... 46

Figure 4-9: Manifold pressure vs RPM ...................................................................... 48

xiv

LIST OF TABLE

Table 2-1 : Synthetic lubricant: Advantages compare to mineral oils ......................... 7

Table 2-2 : SAE Viscosity (Richard, 2013) ............................................................... 10

Table 3-1: Sampling Table ......................................................................................... 22

Table 3-2: Engine Specification ................................................................................. 22

Table 4-1 : Type of gas and effect of living life and environment ............................ 30

Table 4-2: Table of HC at 800 RPM (Idle) ................................................................ 31

Table 4-3 : Table of HC at 3000 RPM (Top) ............................................................. 31

Table 4-4 : CO at 800 RPM (Idle) ............................................................................. 33

Table 4-5: CO at 3000 RPM (Top) ............................................................................ 33

Table 4-6: CO2 at 800 RPM (Idle) ............................................................................ 35

Table 4-7: CO2 at 3000 RPM (Top) .......................................................................... 35

Table 4-8: NOx at 800 RPM (Idle) ............................................................................ 37

Table 4-9: NOx at 3000 RPM (Top) .......................................................................... 37

Table 4-10: O2 at 800 RPM (Idle) ............................................................................. 39

Table 4-11: O2 At 3000 RPM (Top) .......................................................................... 39

Table 4-12: AFR at 800 RPM (Idle) .......................................................................... 41

Table 4-13: AFR at 3000 RPM (Top) ........................................................................ 41

Table 4-14: Engine temperature at 800 RPM (Idle)................................................... 43

Table 4-15: Engine temperature at 3000 RPM (Top) ................................................ 43

Table 4-16: Intake air temperature at 800 RPM (Idle) ............................................... 45

Table 4-17 :Intake air temperature at 3000 RPM (Top) ............................................ 45

Table 4-18: Manifold Pressure at 800 RPM (Idle)..................................................... 47

Table 4-19: Manifold Pressure at 3000 RPM (Top) .................................................. 47

Table 5-1: Average value of gas emission ................................................................. 50

Table 5-2 : Average data reading ............................................................................... 52

Table 5-3: Average ratio of AFR ............................................................................... 53

xv

LIST OF SYMBOLS AND ABBREVIATIONS

API American Petroleum Institute

CCS Cold Crank Simulator

CO Carbon Monoxide

CO2 Carbon dioxide

HC Hydrocarbon

HTHS High temperature high shear

I.C Internal Combustion

MAPM Member of the Association for Project Management

NOx Nitrous Oxide

O2 Oxygen

OEM Original equipment manufacturer

PAO Poly alpha olefins

PIO Poly internal olefins

SAE Society of Automotive Engineers

ZDDP Zinc dialkyl dithio phosphates

1

CHAPTER 1 INTRODUCTION

1.0 Background

This study was to define the effect of engine oil viscosity to the engine

performance of the engine car. Motor oil, engine oil, or engine lubricant is lubricants

that are used for lubrication of internal combustion engines. The main function of

these lubricants is to clean, reduce wear on moving parts, prevent corrosion, cool the

engine by carrying heat away from moving parts and improve sealing. Engine oils

are derived from petroleum-based and non-petroleum-synthesized chemical

compounds. Engine oils today are mainly blended by using base oils composed

of hydrocarbons, polyalphaolefins (PAO), and polyinternal olefins (PIO). Oil crucial

to capable of flowing at low temperatures, so that it gets around the engine in a

fraction of a second at start-up and must protect engine components at high

temperatures without evaporating or carbonizing and maintain adequate oil pressure.

The performance of an engine is measured by fuel consumption, power output,

durability, and emissions. Today's engines are computer controlled and regulate the

air / fuel delivery, ignition timing, and emissions. There are a few calculation that

can show the performance of the engine such as fuel consumption, gas emission,

thermal efficiency, torque and horsepower that will be tested in this experimental

study.

2

1.1 Problem Statement

Nowadays, the engine oil company have produced and sell many types and

viscosity of engine oil. We can see at the market to many choice of engine oil have

been displayed. They claim that this new and fresh formulated engine oil have added

additive that can improve your engine life span, engine performance, fuel

consumption and many others good effect. This mineral base type, semi synthetic

and fully synthetic have added additive such as zinc dialkyldithiophosphate,

molybdenum disulfide and phenols to get low fuel consumption, anti-wear effect

and retard the degradation of the stock oil by oxidation. But car manufacturer or

engine manufacturer has stated that not all types of this engine oil can be used for our

car engine. There are specific viscosity and type of base oil we can use for our car

engine.

For this project, the study was held to identify why such claim were made by

car manufacturers and made analysis on the different viscosity of engine oil to engine

performance to prove their claim.

1.2 Objectives

The function of an engine oil is to create and maintain a lubrication film

between two moving metal surfaces and this function is very much dependant on the

viscosity of the oil itself .Without oil your engine and other moving parts would wear

out very quickly. Engine oil viscosity is not within specified viscosity range, a

condition known as insufficient lubrication will occur, resulting in increased friction,

wear and heat. This wear, heat and friction will cause the engine cannot perform its

maximum and reduce its power slightly.

The objective of this study is as follows:

1. To study the characteristic of engine oil

2. To analyse the performance of the engine based on engine oil viscosity.

3

1.3 Scope

The scopes of this project starts from finding the type of engine oil, find the

engine used for the test and find the suitable test that can show the engine

performance that can be used in this study. Overall scopes of the project are stated

below.

1.3.1 Engine Oil

1. Mineral base (20w-50)

2. Semi-Synthetic (10w-40)

3. Fully-Synthetic (5w-40) engine oil.

1.3.2 Engine

1. 1.3 L Campro four-stroke combustion engine (petrol) .

2. Total displacement: 1,332

3. Bore: 76 mm (3.0 in)

4. Stroke: 73.4 mm (2.9 in)

5. Max output (/rpm) 70 kW (95Ps; 94 hp)/6000

6. Max torque (/rpm) 120N.m (89 lb.ft) /4000

1.3.3 Test Method

1. Gas Emission Test using Exhaust Gas Analyzer

2. LAUNCH X431Scanner Tool

4

CHAPTER 2

Literature Review

2.0 Introduction

This section will discuss about the theories and previous research of this

project in detail. Besides that, it also explains about the method that will be used in

this project

2.1 Lubricant

The lubricant uses have been tracked from ancient of Egypt thousands of

years ago. The ancient of Egyptians shows that the anaglyph inside recorded that

people at the time used lubricant in the form of water to help carry the monument.

Lubricant also has the function of transmitting forces, heating or cooling the surfaces

and transporting foreign particles. The perfect lubricant would not have no friction,

allow no wear and be able to operate at any temperature for any length of time

without any change in its properties (Jackson, A. , 1987). Lubricant also acts as a

substance introduced to reduce friction between surfaces in mutual contact, which

effectively reduces the heat generated when the surfaces move.

In the early 20th century, the lubricant additives began with the use of sulfur

in mineral oil and fatty oil to improve lubrication under high loads. The nano

hardness and the modulus of the friction surface are increased by 67 and 90%,

respectively by using the additive because the additive have improved the surface

mechanics properties of steel-steel friction pair (Yu et al., 2007).

5

Several lubricant attributes which include the level of toxicity, biodegradability and

the products of biodegradation. This has posed a constant threat to the ecology and

vast ground water reserves. Demand for environmentally friendly lubricants are

increasing because of the high concern for environmental protection (Azhari et al.,

2015). For lubricant oils analysis, their chemical composition and size of particles in

wear remains could determine the method of choice. Based on this fact,

environmentally adapted lubricants have become very important (Alves, 2012).

2.2 Mineral oil

Mineral oil or also known as base oils, mineral base oils or lubricant base oils

are chemical substances produced from naturally occurring crude petroleum oil

(Nehal, 2013). Mineral oil refined recomplex and variable mixtures of straight and

branched chain aromatic hydrocarbons, naphthenic and paraffinic have the range of

300-600°c for boiling points (Halder, 1984). Firstly crude oil is distilled atmospheric

pressure and then under high vacuum distillates and residual fractions that can be

further refined from petroleum crude oil.

To get a proper lubrication often are made with a long carbon chain 30 plus

generally recommended for a mineral oil in addition of carbon and hydrocarbon. The

lubricant contains sulphur oxygen nitrogen, this carbon chain carbon and hydrogen.

Mineral or petroleum oils are basically lower molecular weight hydrocarbons

with about 12 to 50 carbon atoms. As they are cheap, available in abundance and

stable under service conditions, hence they are widely used. But the oiliness of

mineral oils is less, so the addition of higher molecular weight compounds like oleic

acid and stearic acid increases the oiliness of mineral oil (Halder, 1984).

6

2.3 Synthetic Oil

Synthetic oil is a lubricant consisting of chemical compounds that are

artificially made (synthesized). Synthetic lubricants can be manufactured using

chemically modified petroleum components rather than whole crude oil, but can also

be synthesized from other raw materials. Synthetic oil is used as a substitute for

lubricant refined from petroleum when operating in extremes of temperature,

because, in general, it provides superior mechanical and chemical properties to those

found in traditional mineral oils.

There are three major classes of synthetic base stock; hydrocarbon, organic

ester and plyglycols (Jackson, A. ,1987). An example for hydrocarbon are

polyalphaolefins, polysobutenes and alkylated aromatics. Low yield process and

expensive raw material were the main reason for unpopular uses of hydrocarbon in

the past. For organic esters, the usually chemical uses in lubricant industry are

dibasic acid esters and polyol ester but the main advantages of esters are low

temperature gelation and high temperature deposits due to glycerine portion of the

molecule. Polyglycol such as ethylene oxide and propylene oxide previously used as

brake fluids but now available as lubricant base stock.

Synthetic lubricants 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 .Usually, special

synthetic lubricants are developed for some purpose demands. For example,

conventional mineral-oil based lubricants could not meet extremely low- (Arctic) or

high-temperature operations and fire resistance requirements.

Synthetic base oils, a complex mixture of hydrocarbons, are the result of a

carefully controlled chemical reaction process that produces a pure chemical of pre-

selected composition (Chevron,2013). This reaction process produces an unlimited

variety of products. Many synthetic-based lubricants are formulated with additives

similar to those in mineral-oil based lubricants. However, some synthetics require

newly developed additives. This is true of the fully formulated lubricants for internal

combustion engines and heavy-duty gear cases. Various types of synthetic-based oils

7

used to formulate synthetic lubricants have certain advantages over conventional

mineral-oil based products. These advantages are low pour point, volatility and

toxicity. It also has a high viscosity index, oxidation stability and flash and fire

points.

Table 2-1 : Synthetic lubricant: Advantages compare to mineral oils

Synthetic Base Type Main Advantages Applications

Alkylbenzenes Low temperature

performance

(Refrigeration) compressor

oils mineral oil-like solvency

Polyalphaolefins Wide temperature

performance range, low

volatility

Engine oil, gear oils,

hydraulic oils

Diesters Wide temperature

performance range, low

volatility

Gas turbine oils, air

compressor oils, Hydraulic

oils

Phosphate Esters Fire resistance Fire-resistant hydraulic

fluids

Polyalkylene Glycols Wide temperature

performance raneg,

hydrolytic stability, frictional

properties

Gas compressor oil, gear oils

Polyolesters Wide temperature

performance range, low pour

point

Jet engine oils, refrigeration

compressor oils (chlorine-

free refrigerants)

2.4 Semi-synthetic oil

Semi-synthetic oils are blends of mineral oil with no more than 30% synthetic

oil designed to have many of the benefits of synthetic oil without matching the cost

of pure synthetic oil. Motul introduced the first semi-synthetic motor oil in 1966.

Lubricants that have synthetic base stocks even lower than 30% but with high-

performance additive packs consisting of esters can also be considered synthetic

lubricants. In general, a ratio of the synthetic base stock is used to define commodity

codes among the customs declarations of tax purposes.

8

Other base stocks help semi-synthetic lubricants like 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 a 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 paraffin.

2.5 Viscosity

For any oil lubrication system, oil viscosity is considered as the most

important parameter. One should always ensure that the viscosity of the oil in use

meets OEM recommendations. The main function of a lubrication oil is to create and

maintain a lubrication film between two moving metal surfaces and this function is

very much dependant on the viscosity of the oil itself.

Often, when the oil viscosity is not within specified viscosity range, a

condition known as insufficient lubrication will occur, resulting in increased friction,

wear and heat. Viscosity can be defined as the measurement of fluid internal

resistance to flow at a specified temperature. Low viscosity engine oil can improve

the fuel economy by lessening the friction between the engine components that

relatively moves in action. (Sae Il Jeon et al.,2007). Engine oil seal frictional torque

has increased in proportional to the shaft rotational speed for all three engine oil

grades.

9

Engine oil seal frictional torque decrease due to the usage of low viscosity

engine oil was confirmed. Also, the leak free performance of the engine oil with the

seal was satisfying the criteria for the life limit durability test. Thus, low viscosity

engine oil usage to improve the fuel economy not only decrease the frictional loss of

the engine oil seal, but also have no defect in the performance of the leak free

function. The automotive industry today is confronted with the pressing challenge of

improving the fuel consumption with the onset of the global squeeze on energy

supplies and rising fuel prices. In particular, the engineering activities for improving

the fuel economy is accelerated due to the global trend of establishing a far more

cutting edge regulation on the fuel emission. Since the fuel economy improvement is

directly linked with decreasing the CO2 which is the main factor for the greenhouse

effect, it is an essential demanding technology in terms of environment.

The engine oil is necessary to decrease the friction and the wear of the

relative dynamic contact movements of the parts within the engine. But, when high

viscosity engine oil is being used for the engine, frictional loss due to the high

viscosity is inevitable. To decrease these frictional losses, researches over using low

viscosity engine oil to improve the fuel economy is in action. On the other hand,

problems due to the low viscosity engine oil take place. When using the low

viscosity engine oil, load capacity defect and wear increase due to oil film strength

decrease takes place among the valve train, crank train and engine bearing which are

key parts in terms of tribology. Therefore, it is necessary to use the low viscosity

engine oil for fuel economy improvement, but excessive lowering of the viscosity

can arouse the adhesion of the various engine parts. It is of utmost importance to

consider the engine characteristic for the optimization of the engine oil viscosity (Sae

Il Jeon et al,. 2007).