South Dakota State University Open PRAIRIE: Open Public Research Access Institutional Repository and Information Exchange Agricultural Experiment Station Circulars SDSU Agricultural Experiment Station 6-1964 Selection of Motor Oil H. Waelti South Dakota State University D. L. Moe South Dakota State University Follow this and additional works at: http://openprairie.sdstate.edu/agexperimentsta_circ Recommended Citation Waelti, H. and Moe, D. L., "Selection of Motor Oil" (1964). Agricultural Experiment Station Circulars. Paper 189. http://openprairie.sdstate.edu/agexperimentsta_circ/189 This Circular is brought to you for free and open access by the SDSU Agricultural Experiment Station at Open PRAIRIE: Open Public Research Access Institutional Repository and Information Exchange. It has been accepted for inclusion in Agricultural Experiment Station Circulars by an authorized administrator of Open PRAIRIE: Open Public Research Access Institutional Repository and Information Exchange. For more information, please contact [email protected]. Circular 163 June 1964 Selection of MOTOR OIL Agricultural Engineering Department Agricultural Experiment Station South Dakota State University, Brookings Selection of Motor Oil by Henry Waelti, assistant professor, and Dennis L. Moe, head, Agricultural Engineering Knowledge of different types and CLASSIFICATION MAKES OIL classifications of crankcase oils SELECTION EASY means savings when selecting mo­ For convenient selection of en­ tor lubricants. In many cases farm­ gine oil it is classified in terms of ers take recommendations of deal­ viscosity and service. ers and salesmen when buying oils, because of confusion on types and Viscosity of an oil is its resistance grades, different engines and con­ to flow. A light (thin) oil offers less ditions under which engines oper­ resistance to flow than a heavy ate. ( thick ) oil and therefore has a lower Crankcase oils perform four main viscosity. Viscosity of an oil chang­ functions in internal combustion es with its temperature. It is desir­ engines. They are: able to have as little viscosity I. Lubricating- this is accom­ change as possible with tempera­ plished by forming a pro­ ture change. An oil should be thin tective film between bearing enough to properly lubricate an surfaces to prevent metal to engine when running cold and metal contact. Friction and thick enough for proper lubrication when the engine is running at op­ abrasive wear is reduced. ° erating temperatures of 160-190 F. 2. Sealing - oil forms a seal between piston, rings and Viscosity index of an oil indicates amount of viscosity change in a cylinder wall to prevent loss ° temperature change from 0 to of power and crankcase con­ ° tamination. 210 F. Low viscosity index means a large change and high viscosity 3. Cooling - oil helps to carry index means a small change in ° away a large amount of heat viscosity for 210 F. temperature produced in the engine. change. 4. Cleaning - oil aids in keep­ ing engines clean by holding Viscosity Classification impurities or sediments in The Society of Automotive Engi­ suspension and reducing de­ neers (SAE) has classified oil in posit formation. terms of viscosity by using SAE Some other functions include: viscosity numbers. These are: SAE reducing noise, cushioning shock, 20, 30, 40, 50. SAE 20 is a light and protection of parts. How well (thin) oil and SAE 50 a heavy these functions are performed de­ (thick) oil. These oils have certain ° pends on type and quality of oil specified viscosities at 210 F. Spe­ used in the engine. cial cold weather oils are designat- 2 Selection of Motor Oil J ed by the numbers SAE SW, lOW, The system includes three kinds of and 20vV. They have specified vis­ oil for gasoline and LPG engines cosities at 0 ° F. to assure easy win­ and three kinds of oil for diesel en­ .l ter starting and proper lubrication gines. at low starting temperatures. In the past few years the so­ OIL CLASSIFICATION FOR called multi-grade oils have come GASOLINE ENGINES into general use. They are, for ex­ Service ML. "Service typical of ample, SAE SW:20 and 10W30 oils. gasoline and other spark ignition en­ SAE SW20 has the starting charac­ gines used under light and favorable teristics of SAE SW oil plus the operating conditions, the engines characteristics of an SAE 20 oil at having no special lubrication re­ operating temperatures. These oils quirements and having no design have a higher viscosity index characteristics sensitive to deposit through addition of viscosity index formation." improvers. This service rating includes old­ Multi-grade oils can be used sat­ er, worn engines, driven at moder­ isfactorily in most gasoline burn­ ate r.p.m. and temperature. Stop­ ing internal combustion engines, start type of driving is definitelynot however, the operator's manual in this classification. should always be consulted to make certain that the manufactur­ Service MM. "Service typical of er's recommendations are followed. gasoline and other spark ignition This is especially so for diesel en­ engines used under moderate to se­ gines. In most cases the operator's vere operating conditions, but pre­ manual will tell what viscosity num­ senting problems of deposit or ber to use. Newer engines usually bearing corrosion control when use a lighter oil than older, worn crankcase oil temperatures are engines. In new engines bearings high." are tight and a thin oil is needed to This includes automobiles, farm form a protective film between tractors, trucks, and power units bearing surfaces. In worn bear­ used in moderate conditions under ings a heavier oil with more body speeds and loads that are not ex­ is needed to obtain adequate pro­ cessively high. tection. Service MS. "Service typical of gasoline and spark ignition engines API Service Classification used under unfavorable or severe Today's modern engines are op­ types of operating conditions, and erated under many different con­ where there are special lubrication ditions and use several types of requirements for deposit, wear or fuel. The American Petroleum In­ bearing corrosion control, due to stitute (API) has provided an oil operating conditions or to design classification based on engine de­ or fuel characteristics." sign and construction, operating The majority of spark ignition conditions, and fuel characteristics. engines require MS service oils, es- 4 So11tb Dakota Experiment Statio11 Circular 163 pecially new engines which are engine design makes it impossible equipped with hydraulic valve lift­ to use oils in the DS classification. ers or valve rotators. Also, engines Operator's manuals or lubrication running cold with short operating charts will indicate when Dl VI serv­ periods, start and stop operations ice oil should be used. or engines running hot, overloaded, DS Service. "Service typical of or at high speeds. diesel engines operating under very Examples: long, high-speed trips severe conditions, or having design (car or truck) frequent short trips characteristics of using fuel tending (car or tri.1ck) stop-start type of to produce excessive wear or de­ driving, heavy field work with trac­ posits." tor, dusty conditions, daily chores The most severe service is covered with tractor. by this classification. i\llost diesel OIL CLASSIFICATION FOR farm tractors fall into this category DIESEL ENGINES due to part-load cold operation in Service DG. "Service typical of winter and high temperature and diesel engines in any operation often overload conditions at other where there are no severe require­ times. ew engines with turbo­ ments for wear or deposit control chargers or high sulfur content due to fuel, lubricating oil or to en­ fuel require oils for service DC. gine design characteristics." Sometimes the type of engine con­ Generally most diesel farm trac­ struction requires the use of Dr-.I tors operate under more severe service oils. Consult the operator's conditions than described in DC manual. service. DC service oils can be used for engines running at contin­ HOW API SYSTEM IS USED uous rated loads at moderate tem­ Oil manfacturers label containers peratures and using fuel of low sul­ as to viscosity and service classifi­ fur content. No. 1 diesel fuel has a cation. As there are multi-viscosity sulfur content of less than }% and oils there are also multi-service oils. can be considered a low sulfur For example, an oil could be fuel. marked "For service MM, MS, and Service DM. "Service typical of DC." In such a case the oil meets diesel engines operating under all requirements for each of the very severe conditions or using fuel three classifications. of a type normally tending to pro­ Sometimes, it might be desirable mote deposits and wear, but where to change an engine to a more se­ there are design characteristics or vere classification oil. This can be operating conditions which may done; however, extreme caution is make the engine either less sensi­ a must. For example, changing from tive to fuel effects or more sensitive an ML to an MS oil is not recom­ to residues from lubricating oil." mended in an old engine, because For diesel engines running under MS oil contains detergent and ML DS service conditions but where does not. The detergent, ,vhich is Selection of Motor Oil 5 added to the oil to keep carbon and while MM oil is intended for com­ other particles in suspension, will paratively light service. The extra loosen and clean up carbon deposits additives in the DS oil are reflect­ in the old engine and cause high oil ed in its higher cost. consumption problems. Also, the Here's how additives function loosened deposits can clog oil pas­ sages and filters reducing lubrica­ when added to lubricants or fuel: tion of some parts of the engine. Detergents. They form a coating This danger can be eliminated or around dirt and other particles non­ reduced by changing oil and filters soluble in oil and keep them in frequently until the engine is suspension in the oil.