Tribological Performance of Engine Oil Blended with Various Diesel Fuels

In this study, petrodiesel (D100) and different concentrations of commercial biodiesels (B100, B50, B5) were blended with a commercial engine oil at a fixed volume ratio of 1:9 to investigate the tribological effect of the biodiesels on the antiwear performance of the engine oil. The antiwear performance of the blended oils was evaluated using a Plint TE77 reciprocating ball-on-flat tribometer at room temperature and 150°C. Results show that the antiwear performance of the engine oil blended with petrodiesel is worse than that of the other blended oils with biodiesels at both temperatures. At room temperature, the physical adsorption and local hydrodynamic effects of the blended oils dominate the tribological behavior; at 150°C, the biodiesel seems to promote the growth of a reaction film with the antiwear additives in engine oil and enhance the growth rate of chemical films. However, an excess concentration of biodiesels causes tribochemical wear, thus reducing antiwear performance.     

钙、镁型发动机油复合剂的抗磨性能

用红外光谱、ICP等离子体发射光谱比较了不同类型配方的SJ 15W／40汽油机油在轿车中使用性能的变化，并与SG15W／40的性能进行了比较。结果表明，各种机油对活塞和活塞环的抗磨性能差别不大；对于SI级机油，钙型配方较镁型配方对气缸壁的磨损较小；镁型配方的SI机油对气缸壁磨损大于钙型配方的SG机油。红外光谱分析表明，在所研究的使用期内，各油品的氧化较轻。     

Valvetrain Friction and Wear Performance with Fresh and Used Low-Phosphorous Engine Oils

Continued legislative pressure to reduce automotive exhaust emissions requires an automotive catalyst to operate at its peak efficiency up to 120,000 miles. Catalyst life is shortened by the poisoning of active sites by glazing caused by the deposition of phosphorous. The primary source of phosphorous is zinc dialkyldithiophosphate, an antiwear and antioxidant additive in engine oil. Therefore, the reduction of the phosphorous level in engine oils raises concern for increased wear of engine components. In an engine equipped with a direct acting mechanical bucket-type valvetrain, high contact stress coupled with sliding action at the cam and tappet contact makes it particularly vulnerable to wear. Motored single cam lobe valvetrain experiments were conducted to evaluate the wear protection capability of several 0.05 wt% P containing engine oils while the oil is fresh. The wear protection capability of vehicle drain samples was also evaluated to ensure adequate protection up to the point of oil change. It was observed that used oils provided significantly improved wear protection capability coupled with reduced friction. An analysis of the tappet shim surface showed that the composition of lubricant-derived protective films formed with used oils is very different than that formed with fresh oil, which may very well explain improved wear characteristics and reduced friction with used oils.     

Comparison of the Effects of Biodiesel and Mineral Diesel Fuel Dilution on Aged Engine Oil Properties

Dilution of engine oil occurs when fuel is injected late in the combustion cycle to regenerate the diesel particulate filter used for trapping particulate emissions. Fuel dilution reduces oil viscosity and the concentration of engine oil additives, potentially compromising lubricant performance. Biodiesel usage may compound these issues due to its oxidative instability, and its higher boiling point compared to mineral diesel potentially causes it to concentrate more in the oil sump.

In this work, different amounts of mineral diesel and biodiesel (soy methyl ester, SME) were combined with 15W-40 CJ-4 diesel engine oil in laboratory oil aging experiments. Fuel was added and oil samples were withdrawn at periodic intervals. The oils were analyzed using typical oil analysis procedures to determine their condition, and wear evaluations under boundary lubricating conditions were determined using a high-frequency reciprocating rig (HFRR). Results showed that fuel dilution accelerated engine oil degradation, with biodiesel having a larger effect. However, friction remained unchanged with dilution, and wear actually decreased for fuel-diluted oils after 48 h of aging compared to aging without fuel dilution. Examination of the tribofilms by ultraviolet (UV) and visible Raman spectroscopy as well as Auger electron spectroscopy showed that additional carbon-containing components were present on tribofilms formed from fuel-diluted oils. These fuel-derived components may be responsible for the decreased wear observed.     

Friction and Wear of Low-Phosphorus Engine Oils with Additional Molybdenum and Boron Compounds,Measured on a Reciprocating Lubricant Tester

Previous research has already extensively characterized the effects of a variety of engine oils on engine performance. However, low-phosphorus engine oils, which are of growing importance due to the reduction of automotive emissions, have not been studied much. This paper sets forth the results of an initial investigation involving the effects of low-phosphorus engine oils on the friction and wear characteristics of typical engine cylinder kit components from a 3.8-liter, four-cylinder engine. For these tests, sections of molybdenum-coated piston rings were oscillated against segments of production cast iron cylinder bores. The oils were evaluated under two sets of conditions; i.e., the frequency of 20 Hz and a load of 60 N and a frequency of 40 Hz and a load of 120 N. The friction coefficients were continuously recorded, and the wear depths on the cylinder bore segments were measured at the conclusion of each experiment. The oils consisted of low-phosphorus prototype oil (LPPO) containing 0.05 wt% phosphorus, which is half the amount of ZDDP in GF–3 oils, and the LPPO treated with six different supplemental antiwear, anti-friction additives. The remaining additives in the LPPO were present in the amount required for full GF–3 formulation. The supplemental additives were selected to lower friction and replace and/or enhance antioxidant and antiwear properties lost due to lower zinc dithiophosphate (ZDDP) content. The results of low phosphorus concentration oils were compared to the results obtained with formulated ILSAC GF-3 engine oil. The oils that contained organomolybdenum ester showed the greatest benefit in friction reduction in the two different operating conditions. SEM/EDS/XPS surface analyses on the surfaces run with oils containing organomolybdenum ester showed evidence of molybdenum compound formation on the cylinder bore surface. In addition, antiwear film formation mechanisms due to surface interaction among the ZnDTP, organomolybdenum compounds, and metal oxides are discussed.     

Tribological Study of a Tetrahedral Diamond-Like Carbon Coating under Vegetable Oil–Based Lubricated Condition

Maintaining a clean environment is the major concern of industries that produce fuel and lubricants for automotive applications. Thus, vegetable-based oils are being explored for the preparation of biobased lubricants because of their biodegradability and nontoxicity. Despite their low thermal stability, vegetable oils show better tribological characteristics than mineral oils. Nonetheless, the thermal stability of vegetable oils could be improved by transesterification. In this study, three vegetable-based oils (sunflower, palm, and coconut) were used to investigate the tribological properties of ta-C diamond-like carbon (DLC) coating under DLC–steel contact condition. A BICERI ball-on-a plate tribotesting machine was used to conduct experiments. During the experiment, test contacts of tribopairs lubricated with sunflower oil exhibited better tribological characteristics than those using coconut oil as a lubricant.     

Experimental investigation of porous bearings under different lubricant and lubricating conditions

The performance of porous bearing under different lubricants and lubricating conditions was experimentally investigated in this study. In order to carry out the experiments, a new test rig was designed to determine the tribological properties of based sintered bronze journal bearings that were manufactured by powder metallurgy (P/M) techniques. To determine the effects of lubricating conditions with and without oil supplement (OS) on the tribological characteristics of these bearings under static loading and periodic loadings, some experiments were carried out using different lubricants. In the tests, pure base oil (SAE 20W50), two fully formulated commercial engine oils (SAE20W50) and lubricating oils with commercial additive concentration ratio of3% were used. The worn surfaces of test bearings were examined using optical microscopy. Experimental results showed that the change in friction coefficient was more stable and in smaller magnitude under static loading than that of periodic loading. In addition, the friction coefficient and the wear rate conducted with base oil resulted in higher values than those of fully formulated oils with and without OS lubricating conditions. The experimental results obtained in this study indicated that the correct selection of lubricant and suitable running conditions were very important on the tribological characteristics of porous bearings.     

A Model for the Loss of Oxidative Stability of Engine Oil During Long-Trip Service,Part II: Vehicle Measurements

Using equations developed in Part I, predicted values for the remaining oxidative stability of engine oil were compared to oil analysis results (oxidation induction time by differential scanning calorimetry) of engine oil from vehicle tests. In driving tests, the loss of oxidative stability of the engine oil followed logarithmic decay curves as predicted by the model. In addition, the model compensated for the loss of oxidative stability due to pulling a 900-kg trailer.     

汽车发动机润滑油更换周期的实验研究

本文通过在上海大众、日本尼桑、二汽东风等车辆上，使用１５Ｗ／４０或ＳＤ级汽油机机油，经过经过长期的跟踪试验，定期从试验车辆上抽取油样，在实验室里进行油品理化性能、铁谱和光谱分析，评判油品质量的衰变规律，在对大量实验数据进行分析处理的基础上，利用统计分析的方法，确定润滑油的更换周期。结果表明，合理地确定换油周期，实行按质换油，才能保证科学地使用汽车发动机润滑油。     

Reduced Phosphorus Concentration Effects on Tribological Performance of Passenger Car Engine Oils

Phosphorus is present in engine oils in the form of the antiwear and antioxidation additive zinc dialkyldithiophosphate (ZDDP). Its effects on wear and friction were studied at different temperatures using a high-frequency reciprocating rig (HFRR). The electrically insulating tribofilm formation was measured using an electrical contact resistance (ECR) technique. The wear and friction performance of a fully formulated fresh oil containing 0.05 wt% phosphorus was compared with the corresponding used oil drained from a vehicle. The results show that the wear performance of fresh oils having phosphorus concentration from 0.02 to 0.1 wt% is very similar. Further reduction of phosphorus concentration below 0.02 wt% leads to high wear. The coefficient of friction increases with increased phosphorus concentration at temperatures above 80°C but decreases with increased phosphorus concentration at temperatures below 80°C. The used oil and the fresh 0 wt% P oil running on the original fresh steel surface exhibit higher wear than when both oils were evaluated on a previously formed film from a fresh oil containing 0.05 wt% phosphorus.     

用SRV试验机评价柴油机油摩擦磨损性能

采用SRV 4型摩擦磨损试验机为试验平台,以某商用车公司提供的发动机缸套-活塞环截取件作为摩擦副试验件,以15W-40 CF-4和15W-40 CI-4发动机油为润滑介质,建立评价柴油机油摩擦磨损性能的模拟试验方法,并使用该方法对油品配方中减摩剂的区分性及不同材质活塞环与润滑油的适配性等进行考察。试验结果表明:建立的模拟试验方法能较好地区分出具有优异抗磨性能的柴油机油,同样对油品配方中减摩剂和不同材质活塞环与润滑油适配性等有着较好的区分性,可以作为润滑油品开发者和OEM汽车厂家对油品配方开发和摩擦副材质筛选的模拟评价手段。     

低黏度GF-60W-16发动机油节能摩擦模拟试验

为了进一步提高汽车燃料经济性,ILSAC颁布的节能发动机油规格已发展到黏度更低的GF-6级别。由于GF-6发动机节能台架试验周期长、成本高,为了提高开发GF-6 0W-16汽油机油配方的筛选效率,利用摩擦模拟试验分析0W-16汽油机油的摩擦润滑性能,并采用综合分析法研究摩擦模拟试验结果和发动机节能台架结果的相关性。结果表明：汽油机油配方中各添加剂之间的协同效应对其节油率和摩擦润滑性能产生显著影响,有机钼添加剂含量多的低黏度GF-6 0W-16汽油机油比参比油GF-5 0W-20更具减摩作用;试验温度激发汽油机油中有机钼减摩剂进一步发挥作用,降低摩擦因数;所建立的摩擦模拟试验综合分析法能够较好地预测低黏度GF-6润滑油节能台架试验结果。     

基于油液分析的注塑机的状态监测

本文对一家汽车安全带生产厂的注塑机，冲压机进行了基于油液分析的状态监测，注塑机和冲压机是该厂的重要进口设备。为了获得注塑机运行状况的有关信息以及在该厂进行设备的现代管理视情维修。对该厂家注塑机、冲压机的油液分析持续了一年的时间，在监测中使用了多种监测技术，如：铁谱分析、发射光谱分析、理化指标分析、研究结果表明，使用综合油液分析技术对设备运行状态进行监测，对防止注塑机，冲压机的重大事故和避免代价高昂的事后维修有重要的意义，并对推进该厂的现代设备管理视情维修作出了重要的贡献。     

Coke Formation from Aircraft Turbine Engine Oils: Part I — Deposit Analysis and Development of Laboratory Oil Coking Test

The authors report here the results of a study undertaken to determine how aircraft engine oil degrades to form coke in static films on engine components and the impacts of additives and surface materials upon the coke production processes. The research is presented in two parts. This first paper deals with the initial research to develop a simple laboratory oil-coking test capable of monitoring antioxidant depletion, oil degradation, and coke formation of stressed aircraft turbine engine oils. Details of the analytical chemistry experiments performed on the stressed samples to quantitate the percentage of oil, polymer dissolved in the oil, and insoluble coke are also presented. The second paper (Part 2) (I) deals with more quantitative measurements of the degradation of thin layers of oil on heated surfaces. Effects of different oils and surfaces are explored.

The results presented in Part I show that simple open-vial laboratory tests involving thin films of oil produce polymer and coke similar to the deposits seen on failed face seals taken from operating aircraft engines and isolated from used engine oils. Coking reactions require oxygen to deplete the antioxidant package and to polymerize/decompose the ester basestock of the oil. After the antioxidant package is depleted, the ester basestock polymerizes to form small oil-soluble polymers. As the oil spends additional time at elevated temperature, these polymers increase in molecular weight and change in chemical composition becoming insoluble in the oil, producing deposits. Although the antioxidants inhibit the polymer/coke reactions, the antioxidants are incorporated in the formed deposits increasing the deposit amount. Consequently, these results indicate the proper concentration and choice of antioxidants will allow elimination, not just reduction, of deposits on engine components coated with thin layers of static oil films.     

天然气汽车专用发动机润滑油研究

天然气作为汽车燃料能显著减少排放污染，并具有良好的经济性，但汽车使用天然气作燃料时，会导致发动机功率下降和严重的早期磨损。为适应发动机使用天然气的特点，专门研究了天然气内燃机润滑机，该润滑油经实验室性能评定、模拟试验、发动机台架试验和汽车道路对比试验。     

高性能蜗轮蜗杆油的研制

研制的蜗轮蜗杆油经过MHK-500梯母肯试验并且经分析检测,结果表明,新配制的蜗轮蜗杆油具有优异的摩擦磨损性能,使蜗轮磨损大大降低,油品的抗氧化和抗乳化性能都有大幅度提高。     

A rig test to measure friction and wear of heavy duty diesel engine piston rings and cylinder liners using realistic lubricants

Laboratory tests to evaluate piston ring and cylinder liner materials for their friction and wear behavior in realistic engine oils are described to support the development of new standard test methods. A ring segment was tested against a flat specimen of gray cast iron typical of cylinder liners. A wide range of lubricants including Jet A aviation fuel, mineral oil, and a new and engine-aged, fully formulated 15W40 heavy duty oil were used to evaluate the sensitivity of the tests to lubricant condition. Test temperatures ranged from 25 to 100 °C. A stepped load procedure was used to evaluate friction behavior using a run-in ring segment. At 100 °C, all lubricants showed boundary lubrication behavior, however, differences among the lubricants could be detected. Wear tests were carried out at 240 N for 6 h at 100 °C with new ring segments. The extent of wear was measured by weight loss, wear volume and wear depth using a geometric model that takes into account compound curvatures before and after testing. Wear volume by weight loss compared well with profilometry. Laboratory test results are compared to engine wear rates.     

Development of a Methodology to Predict Cylinder Liner Scuffing in the 6V92TA Engine Lubricant Test©

The requirements placed on lubricating oils at the top ring reversal point are becoming increasingly severe due to recent changes in engine technology, most of which are driven by emissions regulations. As a result, revised engine tests to evaluate cylinder liner scuffing are being introduced to engine oil specifications. Despite the high cost and generally poor repeatability of full-scale engine data, no laboratory screener test is commercially available. In the present study, various lubricant characteristics were correlated with the level of scuffing in the Detroit Diesel 6V92TA engine test. Good initial agreement was obtained with lubricant volatility measured at 525°C, which is predicted to be the approximate contact temperature under the most extreme conditions likely to exist during normal operation.

Measurement of lubricant volatility, however, yields no indication of additive response and also appears to become less accurate when applied to unconventional basestocks. As a result, a laboratory-scale wear test was developed to predict scuffing resistance under high stress conditions. The results of the wear and volatility rests are combined using a simple equation to form the Diesel Engine Oil Scuff Test (DEOST). The resulting methodology provides an R² correlation of 70 percent with scuffing measured in the 6V92TA engine and is sensitive to both basestock characteristics and antiwear additives. In addition, the DEOST results indicated that viscosity index improvers provide little benefit under high-temperature operation, an effect commonly observed by failure of petroleum-based multigrade oils in the 6V92TA engine test.     

汽油机油配方对节能发动机试验的影响

介绍了汽油机油节能发动机试验的发展状况,讨论了油品配方对节能性能的影响。发动机试验表明,基础油、粘度指数改进剂及添加剂都是影响汽油机油节能性能的因素,在不同的发动机试验中基础油、粘度指数改进剂、抗氧抗腐剂、摩擦改性剂、清净剂、分散剂的影响存在不同的表现形式,在配方设计中要根据具体的发动机试验来确定。