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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

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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

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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. This is the "cleaned-up." reason why detergent oil discolors much quicker than non-detergent ADDITIVES oil. This discoloring also is a rea­ Additives are substances added son why it is impossible to deter­ to lubricants or fuels to improve mine condition of an oil by color certain physical or chemical prop­ As long as particles stay in suspen­ erties or to reduce or eliminate sion they do not deposit on bear­ some undesirable properties. ·when ings and other surfaces. This re­ an additive functions by a physical sults in a cleaner running engine. means, it simply mixes physically Rust and Corrosion Inhibitors. with the lubricant or fuel. vVhen Main reason for adding these com­ the additive acts in a chemical way pounds is to prevent corrosion of it reacts with the lubricant or fuel metal surfaces in contact with the chemically and forms a new prod­ fuel or lubricant. This could be the uct. pipe line transporting oil, storage Some widely used additives are: tanks, fuel pumps, bearings, and Detergent other places. Rust and corrosion inhibitor Anti-oxidant Anti-oxidants. These prevent or Anti-foam agent at least slow down oxidation of oil. Metal de-activators Film strength improvers Oxidation rate of oil depends most­ Extreme pressure additives ly on temperature, oxygen, and Viscosity index improver anti-oxidant present. Pour-point depressant Octane improver in gasoline Anti-foam Agent. Oil tends to Many additives are carefully foam when pumped around a clos­ blended into lubricating oils dur­ ed system. If excessive foaming oc­ ing the manufacturing process. curs the oil pump may lose suction. Kinds and amounts added depend Anti-foam agents, which are most­ on severity of the service of an oil. ly silicone compounds, tend to For example, an oil for DS service break up foaming of an oil. This is has many more additives than an extremely important for oil in the oil intended for MM service. A DS hydraulic system of a tractor be­ oil is intended for the most severe cause of high pressures and heavy running conditions of an engine, churning. 6 So111b Dakota Experime111 Statio11 Cirwlar 163 Metal De-activators. When oil are sold. Some advertised claims oxidizes, certain products of oxida­ about these products, such as re­ tion react with the metal in the duced engine wear and friction, engine. This reaction may form increased power and performance, soluble products which can act as increased gas mileage, and freeing catalysts and speed up the oxida­ sticky valves, are appealing. tion process. Copper and bronze, Most "treatments" include a pe­ used in bearings, are especially troleum base with chemicals added. susceptible to oxidation. Metal de­ Some have a thinning effect on the activators usually act as a de-oxi­ oil which also makes the engine dizer. They prevent oxidation of the oil in the first place and also start easier in cold weather. Similar combine with oxidation products effects can be obtained by using to make them inactive. an oil of a lower SAE number. Other additives have a thickening Film Strength lmprovers and effect which usually tends to re­ Extreme Pressure Additives. In duce oil consumption. If a thicker general, these additives prevent oil is desirable it can simply be re­ metal to metal contact between placed by an oil of higher SAE moving parts subjected to extreme number using SAE 30 in place of loads which might force the lub­ SAE 20 for example. �fany com­ ricant out from between the sur­ mercial treatments contain deter­ faces. They are used mostly in gear gents, rust inhibitors and other use­ lubricants but may be in engine lub­ ful additives. Generally these use­ ricants. ful additives are mixed in quality Viscosity Index Improver. Vis­ motor oil during the manufactur­ cosity index improvers reduce the ing process. amount of viscosity change for a ° Oil manufacturers must improve 210 F. temperature change. For ex­ their lubricants to meet engine re­ i ample, a 5\\120 oil is a very light quirements, competition, and the oil with a V.I. improver added. At API classification standards. This is low temperatures it will act like a why many additives are put into SAE 5 oil and at high tempera­ lubricants during the manufactur­ ture like a SAE 20. ing process. Extra additives added later may actually be harmful by up­ COMMERCIAL ADDITIVES setting the chemical balance of the '.'vlarketing crankcase oil and fuel oil. It is therefore also unwise to additives that are used directly by mix different types and brands of the farmer or motorist has become oil. Engine manufacturers usually a multimillion dollar business. void the warranty on engines if These are generally available damage occurs due to improper where other oil and fuel products use of lubricants. Selectio11 of Motor Oil 7

OPTIMUM ENGINE PERFORMANCE

To help assure best continuous engine performance follow these suggestions: !. Consult the operator's manual when se­ lecting AP! Classification and SAE number of a motor oil for a particular engine. 2. Purchase oil that meets AP! standards. La­ bels on containers indicate AP! classifications. 3. Service the engine as recommended in the operator's manual. Follow instructions on adjustments, air and oil filter cleaning and re­ placement, crankcase draining. 4. Run engine in the proper operating tem­ perature range. 5. llse only high quality fuel.