A Development of Four-stroke Engine Oil Using Palm Oil as a Base ...

The 2 nd Joint International Conference on “Sustainable Energy and Environment (SEE 2006)”C-026 (O) 21-23 November 2006, Bangkok, ThailandA Development of Four-stroke Engine Oil Using Palm Oil as a Base StockKraipat Cheenkachorn * and Isarawat UdornthepDepartment of Chemical Engineering, King Mongkut’s Institute of Technology North Bangkok, Bangkok, ThailandAbstract: Environmental concerns have increased the interest in biodegradable lubricants. This causes many lubricant manufacturersto reconsider vegetable oils as base stocks. The primary efforts of this study have focused on formulating environmentally friendlylubricants for four-stroke engines which are widely used in Thailand. Palm oil was selected to be a candidate due to its largeproduction in the country. Various blends of palm oil and a petroleum base stock were conducted at different compositions. Anadditive package was added to improve some properties. Physical and chemical properties of the blends were then evaluatedincluding viscosity, viscosity index, flash point, foaming characteristics, and wear test. Compared to a conventional lubricant, thepalm-oil based lubricant shows a promising performance in most tested properties.Keywords: Biodegradable Lubricant, Four-stroke Engine, Palm Oil1. INTRODUCTIONVegetable oils and animal fats have been used as lubricants for long time since 1650 B.C. For example, Egyptian chariot wheelswere lubricated by animal tallow while whale fat was widely used as a lubricant for some equipment and machinery [1]. Thediscovery of petroleum oil in the late 1800s resulted in replacement of whale oil for lighting and eventually mineral oils became theprimary base stock for many lubricants due to price and overall performance [2]. However, vegetable oils and animal fats continuedto be used as lubricants but mostly in specialty applications.Early this century, environmental concerns have increased interest in lubricants that are biodegradable. Since vegetable oils andmost esters are more biodegradable than mineral oils, worldwide attention on the biodegradability of lubricants has caused manylubricant manufacturers to reconsider vegetable oils as base stocks. Many studies have looked at the possibility of replacing mineraloils with vegetable oils [3-4]. When vegetable oils are used as base stocks for lubricants, they exhibit good lubricity and highviscosity index (VI). However, their oxidative stability and low temperature properties are worse that those of petroleum-basedlubricants. Vegetable oils enter into the manufacture of lubricants, medicines, cosmetics, detergents, and of course many foodproducts. Soybean oil, for example, is used in plasticizers and detergents, and castor oil in the lubricants, pharmaceuticals, andcosmetics. Corn and soybean oil find use in food products in the United States, and rapeseed oils are frequently used as base stocksfor lubricant manufacture in the North America and Europe [5-6]. Palm oil is one of economical plant oils which is promoted inThailand to solve the current oil price crisis. Most of palm oils are currently used as food consumption and biodiesel production.However, the use of palm oil as a lubricant base stock has not been focused.In southeast Asia, motorcycles are popular because of their convenience and affordable price. More than 15 million motorcyclesare currently used in all regions of Thailand [7]. The number of this vehicle is still increasing every year. Compared with truck orcar engines, motorcycle engine are much smaller and lighter in weight. Therefore, motorcycle engines produce a lot of power.Modern four-stroke motorcycle engines can produce a peak power at about 15,000 rpm [8]. The emission standards across the worldare tightening and the motorcycle original equipment manufacturers (OEMs) are shifting from two-stroke to four-stroke enginetechnology. So, it is challenging to formulate a biodegradable lubricant for four-stroke motorcycle engines.2. METHODOLOGYThe primary purpose of this experimental study is to determine an appropriate composition of a biodegradable lubricant for fourstrokemotorcycle engine using palm oil as a base stock. Various blends of palm oil and mineral oil were prepared prior to thephysical property tests. Palm oil (palm-olein) was obtained directly form a refinery in Krabi, Thailand. Mineral oil and proprietaryadditive package were acquired from PTT Public Co. Ltd., Thailand. The mixture of palm oil, mineral oil, and the additive wereprimary mixed in a 500-ml flask with a magnetic stirrer to obtain and homogenous blends. The recommend dosage of the additive is7.8%, wt for all blends. The lubricant properties were conducted using reference standard methods published by American Societyfor Testing Materials (ASTM), as shown in all table of results.3. RESULTS AND DISCUSSION3.1 Viscosity testThe primary effort of this research is to formulate a biodegradable lubricant for four-stroke motorcycle engine oil, graded SAE 40.Based on SAE specification, the viscosity of the formulated oil must be achieved. The corresponding viscosity at 100 °C for SAE40is 12.5 to 16.3 cSt. [9]. The desired viscosity was set at 15 cSt for this experiment. The blends of palm oil, mineral oil, and theadditive were mixed and showed homogenous phase. No phase separation and sedimentation were observed after three-monthstorage. Tables 1 and 2 show the results of viscosity and viscosity index, respectively. Viscosity of mineral oil is higher than that ofvegetable oil at both conditions. Blend No. 1 (45% Palm oil and 55% Mineral Oil) was randomly mixed to predict the viscosity of theblend. The result shows that the desired viscosity was not reached. Therefore, Blends 2 and 3 were performed by the addition of theadditive package. However, the desired viscosity of those blends was not accomplished.Blends 4-7 were made by the adjustment of the compositions of vegetable oil and mineral oil while the additive dosage was kept at7.24 %wt. The results show as an increase of palm oil content and a decrease of mineral oil content result in a decrease of viscosityCorresponding author: kpc@.kmitnb.ac.th1

The 2 nd Joint International Conference on “Sustainable Energy and Environment (SEE 2006)”C-026 (O) 21-23 November 2006, Bangkok, Thailandof the blends. The opposite trend was observed for Blends No. 7-10. This is due to the fact that viscosity of mineral oil is quitehigher than that of vegetable oil.Looking at the viscosity index which shows the effect of temperature change on the viscosity of the oil, palm oil shows higherviscosity index than mineral oil. This is attributed to the fact that the molecular weight of palm oil is more consistent than that ofmineral oil. The molecular interaction of vegetable oil also results in oil that has higher viscosity index. Oil with high viscosity indexcan resist excessive thickening when the engine is cold. This results in a better engine starting and promoting prompt lubricationcirculation [10]. It also prevents an excessive thinning when the engine is hot and thus provide full lubrication to protect the rubbingsurfaces. Therefore, vegetable oil can provide this advantage when used as a base stock for lubricantsBlendsNo.Table 1 Viscosity of various blends (ASTM D445)Compositions (wt%)Viscosity at 100 C° (cSt)% Palm oil % Mineral oil % Additive1 45.00 55.00 0 8.082 41.74 51.02 7.24 8.743 40.91 50.00 9.09 11.094 55.66 37.11 7.24 16.065 60.30 32.47 7.24 14.716 64.94 27.40 7.24 12.787 57.90 34.30 7.80 13.608 52.90 39.30 7.80 14.459 50.60 41.60 7.80 15.0010 41.20 51.00 7.80 16.80Table 2 Viscosity (ASTM D445) and Viscosity Index (ASTM D2270) of selected blendsBlends Viscosity at 100° C (cSt) Viscosity at 40° C (cSt) ViscosityIndex100% Palm oil 8.65 42.66 187.00100% Mineral Oil 32.51 503.40 96.15Blend No. 9 15.04 111.60 140.00Commercial Oil 15.00 151.6 99.003.2 Flash pointAfter the blends of palm oil and mineral oil were made and the desired viscosity was reached, Blend No. 9 was selected for furtherproperty tests. Table 3 shows the results of flash point of different oils. The flash point property of palm oil and mineral oil isinsignificantly different. As expected, vegetable oil shows high flash point because of the strong interaction among molecules.Selected Blend No. 9 shows unexpectedly lower flash point than that of palm oil and mineral oil. This is possible due to the presenceof the additive package. However, flash point of Blend No. 9 is higher than commercial oil. High flash point is a desirable propertyfor lubricants which leads to the safe transportation and handling processesTable 3 Flash point of selected blends (ASTM D92)Blends Flash Points (° C)100% Palm oil 304100% Mineral Oil 302Blend No. 9 278Commercial Oil 2563.3 Evaporative lossEvaporative loss is one of main properties to be considered for choosing the lubricant base stock. Since lubricant is exposed to asevere condition, it may lose some light weight molecules when it is boiling and the heavy weight molecules are left behind. Thisleads to an increase in lubricant viscosity and thus, makes the oil more difficult to circulate through a lubricating system. Table 4demonstrates that Blend No. 9 shows lower evaporative loss than commercial oil since the sizes of molecules are consistent. One ofthe benefits of using vegetable oil as a base stock for lubricant is low volatility loss which results in lower oil consumption. Lowvolatility lubricants also have the potential for a positive impact on the environment [11].Table 4 Evaporative Loss of selected blends (ASTM D5800-B)BlendsEvaporative Loss (% wt)100% Palm oil N/A100% Mineral Oil N/ABlend No. 9 2.64Commercial Oil 3.072

The 2 nd Joint International Conference on “Sustainable Energy and Environment (SEE 2006)”C-026 (O) 21-23 November 2006, Bangkok, Thailand3.4 Sulfate ashTable 5 shows percent of sulfate ash of selected blends. Sulfate ash is a product from the combustion of sulfur present in fuels andlubricants. Pure palm oil shows extremely low sulfate ash. However, Blend No. 9 shows higher sulfate ash than commercial oil.This is due to the present of additive package which contains sulfur which leads to a high sulfate ash. The result agrees with theprevious study by Colclough [12] which demonstrated that the main additives used in automotive lubricants are zincdithiophosphates (ZDDP). ZDDP can lead to catalytic converter poisoning. Higher sulfate ash oil can contribute to an increaseparticulate matter of the exhaust gas emission. The previous study demonstrated that sulfate may originate from both fuel and oil [13].The general contents of sulfur in fuel and oil are 500 and 5000 ppm, respectively. The consumption ratio of oil to fuel to oil is1000:1. When a sulfur balance is applied to the engine fuel and oil, it was found that 99% of sulfate ash originated from the fuel andonly 1% originated from the oil [14].Table 5 Sulfate Ash of selected blends (ASTM D874)BlendsSulfate Ash (% wt)100% Palm oil 0.007100% Mineral Oil N/ABlend No. 9 1.10Commercial Oil 0.993.5 Foaming characteristicsFoaming characteristics of selected blends were shown in Table 6. Foaming in the lubricant is caused by the presence of water inthe base oil or some chemicals. The results show that Blend No. 9 shows relatively higher foaming characteristics than commercialoil for all sequence. This is attributed to the fact that the antifoam agent in this additive package did not perform well with vegetableoil. The new additive package is recommended to be investigated. As a result, the use of this formulated blend in such applicationsthat incur foaming should be avoided since foaming increases oxidation and reduces the oil flow to the bearing [10].BlendsTable 6 Foaming Characteristics of selected blends (ASTM D892)Foaming Characteristics (mL/mL)Sequence I Sequence II Sequence III100% Palm oil 210/0 N/A/0 60/0100% Mineral Oil N/A N/A N/ABlend No.9 490/310 300/N/A 190/10Commercial Oil 20/5 240/0 10/03.6 Wear scarTable 7 shows wear diameter of selected blends. The results show that wear scar diameter of palm oil is insignificantly differentfrom that of commercial oil. Compared to commercial oil, an addition of additive package in Blend No.9 significantly improves wearscar. Vegetable oil and its additive perform better wear property because the polar head in its structure is able to interact with polarson the metal surfaces. The antiwear additive also forms a protective layer on the metal parts. Therefore, a good lubricity and wearproperty is obtained.Table 7 Wear scar of selected blends (ASTM D4172)BlendsWear scar(mm)100% Palm oil 0.58100% Mineral Oil N/ABlend No. 10 0.34Commercial Oil 0.604. CONCLUSIONThe blends of palm oil, mineral oil, and the additive package were conducted to formulate biodegradable lubricant for four-strokemotorcycle engine. The selected blend consists of 50.60%(wt) palm oil, 41.60 %(wt) mineral oil, and 7.80(%) additive package.The formulated blend shows better properties than commercial oil in terms of viscosity index, flash point, evaporative loss, and wearscar. However, foaming characteristics and sulfate ash are poorer because of the presence of improper additive. This primary showsthat palm oil has a potential as a base stock for four-stroke motorcycle oil.5. ACKNOWLEDGMENTSThe authors gratefully acknowledge the contribution of the Department of Chemical Engineering, King Mongkut’s Institute ofTechnology North Bangkok.3

The 2 nd Joint International Conference on “Sustainable Energy and Environment (SEE 2006)”C-026 (O) 21-23 November 2006, Bangkok, Thailand6. REFERENCES[1] Dowson, D., (1989) History of TribologyNon, Professional Engineering Publishing Ltd, London.[2] Dorinson, A. and Ludema, K.C. (1985) Mechanics and Chemistry in Lubrication Tribology Series 9, Amsterdam, TheNetherlands.[3] Masjuki, H.H., Maleque, M.A.,Kubo, A., and Nonaka, T. (1999) Palm oil and mineral oil based lubricants-their tribological andemission performance, Tribology International, 32, pp. 305-314.[4] Wan Nik, W.B., Ani, F.N., Masjuki, H.H., Eng Giap, S.G. (2005), Rheology of bio-edible oils according to several rheologicalmodels and its potential as hydraulic fluid, Industrial Crops and Products, Article in Press.[5] Goyan, R. L., Melley, R.E., Wissner, P.A., and Ong, W.C. (1998) Biodegradable Lubricants, Lubrication Engineering, 54, (7),pp. 10-17.[6] Fuks, I.G.., Yu, A., Evdokimov, A.A., and Luksa, A. (1992) Vegetable oils and animal fats as raw materials for manufacture ofcommercial, Chemistry and Technology of Fuels and Oils, 4, pp. 203-237.[7] http//:www.dlt.go.th (2006).[8] http//:www.howstuffworks.com (2006).[9] Society of Automotive Engineers (1995) SAE Fuel and Lubricants Standards, Warrendale, Pennsylvania, USA.[10] Mortier, R.M. and Orszulik, S.T. (1997) Chemistry and Technology of Lubricants, Chapman &Hall, Great Britain.[11] Rudnick, L.R. (2005) Synthetics, Mineral Oils, and Bio-Based Lubricants, CRC/Taylor&Francis, Boca Roton.[12] Colclough, T (1987) Role of Additives and Transition Metals in Lubricating Oil Oxidation, Ind.Eng.Chem. Res., 26, pp. 1888-1895.[13] http//:www.osti.gov/fcvt/deer2005/plumley.pdf (2006).[14] http//:www.osd.gov/17.pdf (2006).4