Appl. Chem. Eng., Vol. 29, No. 3, June 2018, 289-297 https://doi.org/10.14478/ace.2018.1001 Article 임영관 이은율 이경묵 나용규 김종렬 한국석유관리원 (2018 년 1 월 5 일접수, 2018 년 2 월 10 일심사, 2018 년 2 월 14 일채택 ) Quality Monitoring for Domestic Distributing Engine Oil Young-Kwan Lim, Eun-Yul Lee, Kyoung-Mook Lee, Yong-Gyu Na, and Jong-Ryeol Kim Korea Petroleum Quality & Distribution Authority, Chungcheongbuk-Do 28115, Korea (Received January 5, 2018; Revised February 10, 2018; Accepted February 14, 2018) 초록자동차용윤활유가국내윤활유시장의 35% 를차지하고있으며, 이중엔진오일이자동차용윤활유의 77% 를차지하고있다. 운전자와엔진보호를위해유통엔진오일의품질이적절하게관리되어져야한다. 하지만 KS제품과합성엔진오일 ( 합성기유가 30% 이상포함된제품 ) 은석유및석유대체연료사업법상품질검사에서제외되어져있다. 본연구에서는국내유통되고있는합성엔진오일 30개제품에대한품질모니터링을실시하였다. 품질모니터링결과, 2개제품이품질이부적합하였는데, 이중 1개제품은해외에서수입한합성엔진오일이며, 다른 1개제품은 KS제품이면서합성엔진오일이었다. 또한고온모사증류시험 (SIMDIST) 을이용해엔진오일의패턴을분석한결과, 해외수입제품몇개를제외하고는대부분일반광유엔진오일의전형적인넓은탄소수분포패턴을보였다. 따라서소비자의피해를예방하기위해 KS제품과합성엔진오일에대한적절한품질관리법규가필요한것으로판단된다. Abstract The vehicle lubricant has captured 35% of the total lubricant market while the engine oil possessed 77% of the vehicle lubricant market in Korea. The suitable quality management of circulating engine oil is thus required for the driver and engine protection. But, KS and synthetic engine oil products (containing over 30% synthetic oil) are exempt to any quality inspections under Petroleum and Alternative Fuel Business Act. In this study, our research group investigated the quality monitoring of 30 kinds of domestic distributing synthetic engine oils. Two kinds of the engine oil showed an off specification from the test results; one engine oil is an imported and the other is a KS synthetic one. Also, the pattern of engine oils were analyzed using SIMDIST (simulated distillation) and the most engine oils had a broad carbon number spectrum, which is a typical of mineral oils except several imported products. Thus, we concluded that relevant laws for the proper quality management of synthetic oils and KS products are needed to be established for preventing consumer s damages. Keywords: engine oil, KS product, synthetic lubricant, quality monitoring 1)1. 서론 아무리정교하게제작된장비 ( 설비 ) 라고하더라도, 움직이는두접촉면에서는반드시마찰이발생되며, 마찰에의한동력손실과마찰 마모로인한고장을방지하기위해장비 ( 설비 ) 에윤활유를사용한다 [1]. 윤활유제품은일반적으로윤활기유 (base oil) 에기능성첨가제를일정비율로혼합하여생산된다. 윤활유제품의주성분인윤활기유는원유를정제하여만든광유 (mineral oil) 와저분자단위체를이용해고분자량으로전환한형태의합성기유 (synthetic base oil) 로구분된다. 합성기유는일반광유의단점을보완한다양한성능 ( 내마모성, 산화 Corresponding Author: Korea Petroleum Quality & Distribution Authority, Chungcheongbuk-Do 28115, Korea Tel: +82-43-240-7973 e-mail: yklim92001@kpetro.or.kr pissn: 1225-0112 eissn: 2288-4505 @ 2018 The Korean Society of Industrial and Engineering Chemistry. All rights reserved. 안정성등 ) 을지니는것으로알려져있다 [2]. 일반적으로합성기유로는에틸렌 (ethylene) 이나 1-데센 (1-decene) 과같은올레핀 (olefin) 형태의단량체 (monomer) 를중합시켜만든 PAO (poly alpha olefin) 가대표적이며, PAO는윤활유산업초기광유의열악한산화안정도등을보완하는고성능윤활기유로알려져있다 [3,4]. 그밖의엔진오일용합성기유로는폴리부텐 (polybutene), 알킬벤젠 (alkylbenzene), 디에스테르 (diester), 폴리올에스테르 (polyolester), 폴리알킬렌글리콜 (polyalkylene glycol) 등이있지만대부분사용량이작다 [5,6]. Figure 1은일반적인윤활유생산공정을나타내고있으며, 원유로부터기인된윤활기유에첨가제를첨가하여생산한일반윤활유와올레핀과같은단량체로부터인위적으로합성된합성기유에첨가제를첨가하여생산한합성윤활유로구분된다. 합성윤활유는일반윤활유에비해비교적비싼가격으로유통되고있다. 국내에서는합성윤활유외에 KS 제품을등록, 판매하고있다. KS 289
290 임영관 이은율 이경묵 나용규 김종렬 Table 1. Specification of Vehicle Engine Oil in Korea[11] Item SAE0W SAE5W SAE10W SAE15W SAE20W SAE25W 20 SAE20 30 (SAE30) 40 (SAE40) 50 (SAE50) 60 (SAE60) Flash Point ( ) over 170 over 170 over 170 over 175 over 180 over 185 over 180 over 190 over 195 over 200 over 205 Cold Cranking Simulator (Pa s) 6.20 (-35 ) 6.60 (-30 ) 7.00 (-25 ) 7.00 (-20 ) 9.50 (-15 ) 13.00 (-10 ) - - - - - Kinematic Viscosity (100, mm 2 over 3.8 over 3.8 over 4.1 over 5.6 over 5.6 over 9.3 5.6~9.3 9.3~12.5 12.5~16.3 16.3~21.9 21.9~26.1 /s) Viscosity Index over 85 over 85 over 85 over 85 over 85 over 85 over 85 over 85 over 85 over 85 over 85 Pour Point ( ) Oxidation Stability (165.5, 24 h) Ratio of Viscosity Increase of TAN (mg KOH/g) -35.0-30.0-25.0-22.5-22.5 Lacquer light light light light light light light light light light light -17.5-12.5-10.0-7.5-5.5-2.5 Figure 1. The process of lubricant production and quality inspection. 표시인증은업계의사내표준화와품질경영을도입, 촉진하고우수공산품의보급확대로소비자보호를위해특정상품이한국산업표준수준에해당함을인정하는제품인증제도이다 [7]. KS로등록된윤활유제품은 3년에한번씩한국표준협회등관련기관의정기심사를받아야하지만, 심사주기가비KS 석유제품에비해매우길다. 국내윤활유시장은해마다증가되고있으며, 그중 35% 가자동차용윤활유로가장큰부분을차지하고있으며, 자동차용윤활유중 77% 가엔진오일이차지하고있다 [8]. 윤활유시장의가장큰비중을차지하고있는엔진오일은국내 외자동차시장의호황에따라계속적으로증가되고있어, 2016년기준 475,088 kl의생산량을보였다 [9]. 이러한엔진오일은 석유및석유대체연료사업법 에따라품질관리상태를확인하기위해정기적으로품질검사를받아야한다. 하지만국내유통되고있는엔진오일의대부분을차지하고있는합성엔진오일과 KS제품은 석유및석유대체연료사업법 에서품질검사제외대상으로정해져있다. 따라서품질검사제외대상에대해서는생산자외에는정기적인품질관리가이루어지고있지않은상태이다. 우리연구팀에서는국내유통되고있는합성엔진오일을고온증류 모사시험 (SIMDIST, simulated distillation) 을통해분석한결과, 합성유로광고, 판매되고있는대부분의엔진오일이합성기유인 PAO가함유되어있지않거나, PAO함량이매우낮다는것을기존에발표하였다 [10]. 하지만기존연구에서는단지 SIMDIST를통해 PAO함량에대한접근을하였으며, 품질에대한접근은하지못했다. 본연구에서는석유및석유대체연료사업법에서품질검사대상은아니지만, 국내엔진오일유통시장의대부분을차지하고있는합성엔진오일제품과 KS제품으로등록, 판매된 30종의엔진오일에대해품질상태를확인하기위해품질모니터링을실시하였다. 2. 실험 2.1. 국내유통엔진오일국내판매량이높은엔진오일에대한품질모니터링을위해 30개엔진오일제품을시중에서구매하였다. 엔진오일은 KS제품또는합성엔진오일로등록되어져있어석유및석유대체연료사업법상품질검사에서제외된제품들로선정하였다. 공업화학, 제 29 권제 3 호, 2018
291 Table 2. Kinds of Engine oil Product for Quality Monitoring Engine Oil Viscosity Engine type KS product Mobil 1 0W20 Gasoline/LPG Fully Synthetic - Mobil 1 0W30 Gasoline/LPG Fully Synthetic - Mobil 1 0W40 Gasoline/LPG Fully Synthetic - Shell Helic Ultra 0W30 G/D Fully Synthetic - Castrol EDGE 0W30 G/D Fully Synthetic - Castrol EDGE Titanium 0W40 G/D Fully Synthetic - KIXX NEO 0W30 Gasoline Synthetic KS Aral Super Tronic 0W40 G/D/LPG 100% Synthetic - MITASU SM Hybrid 0W20 Hybrid 100% Synthetic - ZIC X7 5W30 Gasoline/LPG Synthetic KS ZIC X9 5W40 G/D/LPG 100% Synthetic KS Mobil super 3000 5W30 G/D/LPG Fully Synthetic - KIXX PAO 5W30 Gasoline 100% Synthetic KS ZIC TOP 5W30 Gasoline/LPG 100% Synthetic KS S-oil Seven Gold 5W30 G/D 100% Synthetic KS S-oil Seven Red 1 5W30 Gasoline 100% Synthetic KS Total Quarts INEO 229.31 5W40 G/D Synthetic - Total Quartz 9000 Future GF-5 5W30 Gasoline Synthetic - BP Visco 7000 5W30 G/D/LPG 100% Synthetic - Miratec 5W30 G/D/LPG Fully Synthetic - Miratec 5W40 G/D/LPG Fully Synthetic - Liqui Moly Top Tec 5W40 G/D/LPG 100% Synthetic - KIXX D1 RV 5W30 Diesel Synthetic KS Vavoline Turbo GX10 5W40 Gasoline/LPG Fully Synthetic - Vavoline Turbo GX10 5W30 G/D/LPG Fully Synthetic - ZIC A 5W30 Gasoline Synthetic KS KIXX Ga 7.5W30 Gasoline Synthetic KS ZIC 5000 Power 10W40 Diesel Synthetic KS KIXX Turbo RV 10W40 Diesel Synthetic KS KIXX LPG 10W40 LPG Synthetic KS * G/D : Engine oil for gasoline and diesel engine (universal oil). * G/D/LPG : Engine oil for gasoline, diesel, and LPG engine (universal oil). 2.2. 엔진오일품질분석 2.2.1. 동점도및저온겉보기점도분석동점도는 Cannon Instrument Company, CAV 2000 series의 Cannon 1257 유리제모세관식튜브를이용하여 40 와 100 에서 ASTM D 445 방법에따라측정하였다. 모세관식튜브에는 3개의벌브 (bulb) 가있으며, 벌브사이에온도센서가있어시료약 15 ml를흡입상승시킨뒤, 시료가중력에의해하강하는시간을온도센서로감지함으로써동점도를측정하였다 [12]. 저온겉보기점도는 Cannon Instrument Company의 CCS-2000 series 를이용하여 50 ml의시료를취해해당점도에따라 -35, -30, -25 에서회전자의속도와점도와의함수관계를이용하여저온겉보기점도를측정하였다 [13]. 2.2.2. 인화점및유동점분석인화점은용기에시료 70 ml를채운뒤, Tanaka사의 ACO-T602장비를이용하여클리브랜드개방컵 (Cleveland open cup), KS M ISO 2592 방법에따라분석하였다. 시료의온도를높이면서, 가열된전기코일에의해인화되는최저온도를인화점으로측정하였다 [14]. 유동점 (Pour point) 은 ASTM D 97 방법에의해 Tanaka사의 MPC-602를이용하여측정하였다. 4 ml의시료를용기에채운뒤, 45 로가온한후, 분당 1 의속도로냉각하면서시료가고체상으로전환되어유동되지않는온도를유동점으로측정 (3 단위로측정 ) 하였다 [15]. 2.2.3. 산화안정도및전산가산화안정도는 Yoshida사의 ISOT-D8을이용하였으며, KS M 2021 방법에따라시험하였다. Appl. Chem. Eng., Vol. 29, No. 3, 2018
292 임영관 이은율 이경묵 나용규 김종렬 Table 3. SIMDIST Analytic Instrument and Test Conditions Manufacture Thermo Model Trace GC Ultra Test Method ASTM D 2887 Column 10 m 0.53 mm ID 0.88 µm Oven Temp. Trace GC Ultra Initial; 40, 1 min hold Increase; 15 /min to 360, 10 min hold Detector FID (370 ) 시료컵에일정크기의강판과구리판촉매를넣고, 250 ml의시료를넣은뒤, 165.5 ± 0.8 로승온하여회전막대를 1300 ± 15 rpm으로회전시켜 24 h 동안시료를산화시킨후, 40 에서동점도를측정하여산화전 후에대한동점도변화정도와함께전산가를측정해산화전 후에대한전산가증가정도를측정하였다 [16]. 전산가는 Metrohm사의 805 Dosimat을이용하였으며, KS M ISO 6618방법에의거해분석하였다. 시료 1~2 g의시료를유리컵에취한뒤, 100 ml의용매 (Tol : IPA : Water = 50 : 49.5 : 0.5) 로시료를녹인후, 0.1 N KOH를이용하여적정하여전류값의변환지점을당량점으로인식하여, 시료의전산가를분석하였다 [17]. 레커도 (lacquer) 는산화안정도시험에서사용되는유리막대에윤활유의산화생성물 ( 열화생성물 ) 의부착여부를육안으로확인하였다. 2.3. 고온모사증류시험분석 일반가스크로마토그래피를이용해윤활유분석을할경우, 일부고비점성분이컬럼을통과하지못해분석결과에오류를범할수있다. 고온모사증류시험 (SIMDIST) 은이러한고비점물질에대한분석에적합한분석시험방법으로윤활기유, PAO 및유통엔진오일에대한증류시험분석을위해활용하였으며, 분석장비및시험방법은 Table 3과같다 [18]. 3. 결과및고찰 3.1. 인화점, 저온겉보기점도및유동점품질모니터링 인화점은점화원존재하에서시료를서서히가열하여, 불이붙는최저온도로석유제품의화재안전성과연관되는품질항목이다. 저온겉보기점도는엔진오일의점도기준에따라일정한온도 (-35, -30, -25 ) 에서분석하였으며, 저온에서의시동성과연관되는품질항목이다. 유동점은온도를낮추어시료의흐름성이없는최고온도로저온에서의시동성이나흐름성과연관되는품질항목이다. 국내유통되고있는 30개엔진오일제품의인화점, 저온겉보기점도및유동점에대해품질모니터링을한결과, 모두품질기준에적합하였다 (Table 4). 3.2. 동점도, 점도지수및산화안정도품질모니터링 동점도는시료를자유낙하시켰을때낙하속도로부터산출되며, 자유낙하속도가늦으면, 높은동점도를갖게되며, 높은동점도는윤활성을향상시킬수있으나, 동력손실에따른차량의연비저하를일으킬수있다. 윤활유의동점도는높은온도에서는낮아지고, 낮은온도에서는증가되는데, 온도변화에따라동점도변화값이작을수록높은점도지수를갖게된다. 점도지수가높을수록점도측면에서는좋은윤활유제품으로판단한다. 엔진오일은고온의엔진룸에서장기간사용하기때문에산화안정도가우수해야한다. 엔진오일의산화안정도 Table 4. Test Result of Flash Point, Cold Cranking Simulator, and Pour Point Engine Oil Flash point ( ) CCS (mpa s) Pour point ( ) 1 230 2401 ( -35 ) -57 2 230 5761 ( -35 ) -45 3 218 5456 ( -35 ) -51 4 232 5707 ( -35 ) Below -57 5 230 5254 ( -35 ) Below -57 6 242 5755 ( -35 ) -48 7 226 4721 ( -35 ) -45 8 236 5832 ( -35 ) Below -57 9 218 4929 ( -35 ) -51 10 234 5725 ( -30 ) -39 11 230 5795 ( -30 ) -42 12 226 5021 ( -30 ) -42 13 230 5396 ( -30 ) -45 14 228 5706 ( -30 ) -45 15 236 5446 ( -30 ) -39 16 234 5549 ( -30 ) -33 17 232 6337 ( -30 ) -42 18 242 3661 ( -30 ) -39 19 230 5992 ( -30 ) -39 20 216 5625 ( -30 ) -42 21 232 6075 ( -30 ) -42 22 234 5724 ( -30 ) -39 23 222 2520 ( -30 ) -45 24 232 6417 ( -30 ) -33 25 234 5599 ( -30 ) -42 26 224 5175 ( -30 ) -42 27 234 5763 ( -25 ) -42 28 236 5003 ( -25 ) -39 29 236 4624 ( -25 ) -45 30 262 4519 ( -25 ) -33 는산화전 후의시료에대한점도비와전산가증가를통해판단하며, 점도비와전산가증가가낮을수록산화안정도면에서우수한제품으로판단할수있다. 30개엔진오일제품에대한품질모니터링결과, 점도지수와산화안정도는품질기준에적합하였다. 하지만 22번제품과 30번제품은동점도품질기준이 12.5~16.3 mm 2 /s이지만, 22번제품은 12.13 mm 2 /s, 30번제품은 9.691 mm 2 /s로분석되어, 품질부적합을보였다. 22번제품은해외에서수입되고있는합성엔진오일이며, 30번제품은국내에서합성엔진오일로광고, 판매되고있는제품이면서 KS제품으로등록된제품이다. 공업화학, 제 29 권제 3 호, 2018
293 Table 5. Test Result of Kinematic Viscosity, Viscosity Index and Oxidation Stability Engine Oil Kinematic Viscosity (mm 2 /s) 40 100 Viscosity Index Oxidation Stability (165.5, 24 h) Ratio of Viscosity Increase TAN (mg KOH) Lacquer 1 45.56 8.704 173 0.96-0.07 No attached 2 65.63 11.93 181 0.92 0.15 No attached 3 75.22 13.52 185 0.92-0.36 No attached 4 58.94 17 195 0.96 0.01 No attached 5 70.15 12.22 173 0.97-0.06 No attached 6 77.58 13.06 171 0.98 0.01 No attached 7 62.03 11.17 175 0.96-0.06 No attached 8 76.84 13.08 173 0.96-0.17 No attached 9 42.74 8.114 167 0.96-0.48 No attached 10 64.87 10.82 158 0.96 0.04 No attached 11 83.22 13.67 168 0.92 0.04 No attached 12 65.26 18 174 0.95 0.26 No attached 13 69.75 12.19 174 0.93 0.04 No attached 14 70.30 12.07 170 0.91 0.75 No attached 15 71.95 12.25 169 0.94 0.07 No attached 16 62.71 10.60 160 0.95 0.01 No attached 17 86.31 14.19 170 0.91 0.01 No attached 18 62.92 10.58 158 0.94 0.29 No attached 19 71.23 12.38 174 0.97 0.21 No attached 20 65.85 11.16 163 0.98 1.24 No attached 21 98.67 14.61 154 0.98 0.01 No attached 22 70.84 12.13 170 1.01 0.48 No attached 23 67.08 11.93 176 0.95 0.01 No attached 24 82.96 13.49 166 0.95 0.29 No attached 25 65.78 11.48 170 0.92 0.11 No attached 26 63.66 10.74 160 0.97-0.23 No attached 27 66.57 10.09 136 0.98-0.07 No attached 28 102.0 15.29 158 0.89 0.01 No attached 29 95.80 14.92 163 0.96-0.03 No attached 30 60.37 9.691 144 0.96 0.01 No attached 3.3. 윤활기유및 PAO의 SIMDIST 분석 [10] 광유로부터생산된윤활기유는수천가지이상의분자혼합물이기때문에 SIMDIST를이용해분석할경우, broad한탄소수분포스펙트럼 (spectrum) 이얻어지며, PAO와같은합성유는 olefin의중합반응에의해특정분자로전환되었기때문에 SIMDIST 로분석할경우, 특정성분의 sharp한스펙트럼이얻어진다. Figure 2는광유윤활기유 (Base) 에합성기유 (PAO) 를일정비율로혼합하여, SIMDIST 를분석한결과이다. 분석결과, 광유에합성기유인 PAO가함유될경우, PAO 혼합비율이높아질수록 sharp한 PAO 특정피크가증가되었다. 또한 PAO가 20% 만혼합되어도, PAO의혼합여부를 SIMDIST를통해충분히확인이가능할수있을정도로 sharp한 PAO의특정피크가검출됨을볼수있다. 3.4. 국내유통엔진오일제품 SIMDIST 분석순수한윤활기유와 PAO를일정비율로혼합하여 SIMDIST를분석한후, 국내유통중인 30개엔진오일제품에대해 SIMDIST 분석을실시하였다. 석유및석유대체연료사업법상, 합성유는합성기유가 30% 이상함유되어져야하며, 이들제품에대해서는품질검사에서제외된다. Figure 3에서보는바와같이 Aral Super Tronic제품은전형적인합성기유의특정페턴을보였다. 하지만몇몇해외제품 (Mobil 1, Castrol EDGE, Liqui Moly Top Tec, Aral Super Tronic) 을제외하고, 합성유로광고, 판매되고있는대부분의제품들이광유윤활기유의전형적인 broad한탄소수분포스펙트럼을보였다. 이는합성기유인 PAO가 30% 이상혼합되지않은제품으로판단할수있다. Appl. Chem. Eng., Vol. 29, No. 3, 2018
294 임영관 이은율 이경묵 나용규 김종렬 Base (100%) Base : PAO (8 : 2) Base : PAO (6 : 4) Base : PAO (4 : 6) Base : PAO (2 : 8) PAO (100%) Figure 2. SIMDIST analysis for mineral base oil blended with PAO. Mobil 1 (0W20) Mobil 1 (0W30) Mobil 1 (0W40) Shell Helix Ultra (0W30) Castrol EDGE (0W30) Castrol EDGE Titanium (0W40) Figure 3. SIMDIST analysis for distributed engine oil in Korea. To be continued 공업화학, 제 29 권제 3 호, 2018
295 KIXX NEO (0W30) Aral Super Tronic (0W40) MITASU SM Hybrid (0W20) ZIC X7 (5W30) ZIC X9 (5W40) Mobil Super 3000 (5W30) KIXX PAO (5W30) ZIC TOP (5W30) S-oil Seven Gold (5W30) S-oil Seven Red 1 (5W30) Total Quarts INEO (5W40) Total Quartz 9000 Future GF-5 (5W30) BP Visco 7000 (5W30) Miratec (5W30) Miratec (5W40) Figure 3. Continued. To be continued Appl. Chem. Eng., Vol. 29, No. 3, 2018
296 임영관 이은율 이경묵 나용규 김종렬 Liqui Moly Top Tec (5W40) KIXX D1 RV (5W30) Valvoline Turbo GX10 (5W40) Valvoline Turbo GX10 (5W30) ZIC A (5W30) KIXX Ga (7.5W30) ZIC 5000 Power (10W40) KIXX Turbo RV (10W40) KIXX LPG (10W40) Figure 3. Continued. 4. 결론 국내윤활유시장은계속증가하고있으며, 윤활유시장중에서자동차용엔진오일이차지하는비중이가장높다. 운전자의안전과엔진보호를위해엔진오일에대한품질검사가정기적으로이루어져야하지만, 석유및석유대체연료사업법에서는국내엔진오일의대부분을차지하고있는합성엔진오일과 KS제품을품질검사제외대상으로분류하고있다. 본연구에서는국내판매량이높은엔진오일 30개제품에대해품질모니터링을실시하였다. 모니터링결과 2개제품이동점도에서품질부적합을보였으며, 이들중 1개는해외에서수입, 판매되는합성엔진오일이며, 다른 1개는국내합성엔진오일로생산, 판매되고있을뿐만아니라 KS제품으로등록된제품이다. 또한이들 30개엔진오일제품을대상으로 SIMDIST를분석한결과, 일부해외수입제품을제외한대부분의제품들이합성유로광고, 판매하고있지만광유윤활기유의전형적인 broad한스펙트럼을보임으로써, 합성기유인 PAO가 30% 이하로혼합되고있는것을확인하였다. 따라서기존관련법규의개정등을통해품질검사사각지대에있는윤활유제품 ( 합성유, KS제품 ) 에대한적절한품질관리를함으로써소비자의피해예방이이루어져야할것으로판단된다. References 1. J. M. Lee, Empirical Evaluation of Quality Status and Oil Change Intervals of Lubricants for Vehicles, PhD Dissertation, Chungbuk National University, Cheongju, Korea (2016). 2. Z. A. Wang and Z. R. Zhou, An investigation of fretting behaviour of several synthetic base oil, Wear, 267, 1399-1404 (2009). 3. S. Jiang, S. Li, L. Liu, L. Wang, and N. Mominou, The tribological properties and tribochemical analysis of blends of poly alpha-olefins with neopentyl polyol esters, Tribol. Int., 86, 42-51 (2015). 4. M. Kano, Super low friction of DLC applied to engine cam follower lubricated with ester-containing oil, Tribol. Int., 39, 1682-1685 (2006). 5. I. A. El-Magly, H. K. Nagib, W. M. Mokhtar, Aspects of the behavior of some pentaerylthritol ester base synlubes for turbo-engines, Egypt. J. Pet., 22, 169-177 (2013). 6. J. C. J. Bart, E. Gucciard, and S. Cavallaro, Lubricants; Properties and characteristics, Biolubricants, 24-73 (2013). 7. Korea Agency for Technology and Standards, http://kats.go.kr. 8. Korea Lubricating Oil Industry Association, http://www.kloia.or.kr. 9. Enforcement Rule of Petroleum and Alternative Fuel Business Act, Article 28, Section 1, Korea. 공업화학, 제 29 권제 3 호, 2018
297 10. Y. K. Lim, J. Y. Kim, J. R. Kim, and J. H. Ha, The SIMDIST (simulated distillation) analysis of distributing engine oil, Appl. Chem. Eng., 28, 632-637 (2017). 11. Business Act for Quality Standard, Inspection Method and Inspection Fee of Petroleum Products, Ministry of Trade, Industry and Energy, Korea, 2016-20. 12. ASTM D 445, Standard test method for kinematic viscosity of transparent and opaque liquids and calculation of dynamic viscosity. 13. ASTM D 5293, Standard test method for apparent viscosity of engine oils between -5 and -35 using the cold-cranking simulator. 14. KS M ISO 2592, Determination of flash and fire points-cleveland open cup method. 15. ASTM D 97, Standard test method for pour point of petroleum products. 16. KS M 2021, Testing methods for oxidation stability of internal combustion engine oil. 17. ISO 6648, Petroleum products and lubricant-determination of acid or base number-colour indicator titration method. 18. ASTM D 2887, Standard test method for boiling range distribution of petroleum fractions by gas chromatography. Appl. Chem. Eng., Vol. 29, No. 3, 2018