4.3 ENGINE OIL

The importance of engine oil (often referred to crankcase oil) in a diesel engine cannot be overemphasized.

Engine Oil Requirements Engine

1. Oil must be able to withstand extreme temperatures and shock loads without breaking down. Although it must form a sliding seal between the piston rings and cylinder walls, the oil film must be thick enough to seal but thin enough to minimize fluid friction. It also functions as a semipurifier by holding solid particles in suspension until they are removed by the filter. Some particles are so fine that they cannot be filtered out, and therefore they remain in the oil until it is changed.
2. Effectiveness of the engine oil ultimately extends the life of the engine. To achieve maximum effectiveness the engine oil should possess the following qualities: good wetting ability, correct viscosity, minimum evaporation during service, relative nontoxicity, no damaging sediments, and no tendency to deposit varnish, gum, or sludge deposits. However, unless the air-intake system, the coolant system, and the fuel-injection system are maintained properly; the oil and filters changed regularly; and the engine coolant temperature maintained between 185 and 205°F (85 and 96°C), the engine oil will not perform satisfactorily.
3. Viscosity is the physical property of an engine oil with which the technician is most concerned. Viscosity is a measurement of fluidity or resistance to flow. Fluidity or resistance to flow changes with temperature; therefore its measurement is always related to temperature. Of the many instruments developed to measure viscosity, the one most used by technicians and engineers is the Saybolt Universal viscometer. This viscometer consists of a calibrated reservoir (in which the test oil is placed) with a fixed (universal) orifice heating n ice at the bottom. The reservoir is surrounded by a bath, which is heated by heati coils to bring the test oil to the temperature at which the viscosity of the oil is to measured. A container marked at the 60-cm' level is placed under the orifice. When the test oil reaches the desired temperature; the orifice is opened. The number of seconds it takes for the oil to reach the 60-cm' level is expressed in Saybolt Universal Seconds (SUS), also referred to as Seconds Saybolt Universal (SSU).
4. A recent method of testing the viscosity of engine oil at 210°F [98.8°C] uses a kinematic viscometer tube. A measured amount of test oil is drawn into a viscometer tube and placed into a bath heated to 210°F [98°C]. The time that it takes for the measured amount of oil to flow through the small diameter tube (called a capillary tube) is then recorded. The pressure which causes the flow in this instrument is the height of the column of oil above the tube (gravity) plus the density of the oil. The viscosity determined in this way is called kinematic viscosity. It is expressed in Saybolt Universal Seconds (SUS) and is converted into engineering units, that is, centistokes (cST).
5. Centistoke viscosity is calculated by multiplying the SUS by the correction factor of the visco-meter.
   A recent method of testing the engine oil viscosity at 0°F [-18°C] to simulate cold starting is by measuring, under precise conditions, the shear strength of a film of oil. The measurement is taken at OOF [-18°C] and in centimeters, grams, and seconds. The unit is called a poise (P) or centipoise (cP).
6. The SAE (Society of Automotive Engineers) specifies ranges of viscosity at low and high temperatures. SAE viscosity numbers without the letter "W" are based on 210°F [98.8°C) viscosity. SAE viscosity numbers with the letter "W" are based on 0°F [-18°C] Viscosity.
   MULTIVISCOSITY OIL A multiviscosity oil is one which at a viscosity of OF" [-18°C] falls within the range of one of the W numbers and at a viscosity of 212°F [100°C] falls within the range of one of the non-W numbers. Thus an oil with a viscosity in the range of 1,200 to 2,400 cP at 0°F [-18°C] and in the range of 9.6 to 12.9 cST at 210°F [98.8°C] is a multiviscosity oil of IOW-30. Fig 4.1 shows the three grades of multiviscosity oil for application at different ambient temperature.
7. NOTE Viscosity is the fluidity of the oil and is not a classification of the quality of the oil
   Engine Oil Additives The success of today's engine oils relates highly to the complex
   chemicals (additives) which are blended into the engine oil base stock. Many of the additives affect more than one of the oil's characteristics.
8. Engine Oil Classificatiop, For many years the American. Petroleum Institute (API) provided an engine oil classification system that related to engine operating conditions. However, because of the increasing demands placed on engine oil, the API, in cooperation with SAE, American Society for Testing and Materials (ASTM), and various car, truck, and engine manufacturers published (in 1970) a new engine oil classification system. This system, based on a letter designation, refers to precise engine operating conditions and oil performance properties in'regard to engine design and construction.
   
9. CA An oil used for light-duty diesel engine service to provide protection against bearing corrosion and from high-temperature deposits in naturally aspirated diesel engines.
10. CB An oil used for moderate-duty diesel engine service. It is designed to provide necessary protection against bearing corrosion and from high-temperature deposits in naturally aspirated diesel engines which used higher sulfur fuels.
11. CC An oil used for moderate-to-severe duty diesel and gasoline engine service. Used in motortrucks, industrial and construction equipment, and farm tractors. I provides protection from high-temperature deposits in lightly supercharged diesel engines and also
    lightly from rust, corrosion, and low-temperature deposits in gasoline engines.
12. CD An oil used for severe-duty diesel engine service. It provides protection against bearing corrosion and from high-temperature deposits in supercharged engines when fuels of a wide quality range are used.
13. CE An oil for requirements typical of turbocharged or supercharged heavy-duty diesel engines, manufactured since 1983, and operated under both low-speed high-load and high-speed high-load conditions.

It is strongly recommended that the oil company e.g. Shell, Esso, Caltex, etc be consulted for their particular engine oil to be used based on the specification of the engine manufacturer.
Storing and Handling Crankcase Oils To reduce the risk of contaminating the lubricant, store oil drums indoors, on an oil-drum rack. Always keep the drum heads, taps, measuring cans dispensers, and surrounding area clean. Never use empty anti-freeze, cans for dispensing any oil. Identify each oil clearly to reduce the possibility of dispensing the wrong oil. Use a power dispenser or a separate measuring can for each product. When possible use taps for each drum to prevent damage to the bungs or to prevent lubricant contamination. Bungs and drum heads must be replaced and tightened immediately after use. Use only a bung wrench in order to prevent damage from frequent opening and closing,

Use only lint-free rags when cleaning the dispensers because lint can accumulate and stop oil circulation. If you must store the drums outside, tilt them slightly with the bungs at 3 o'clock and 9 o'clock or lay them on their sides so that water cannot enter. Always wipe up any spilled oil around the drums. Do not use sand or a chemical to soak up the oil. Not only is a chemical a fire hazard, but it may get into the oil.

often wrong oil is accidentally used to top up engine crankcase. There is one effective way to prevent this and that is to use colour coding. For engine oil, paint the, cap and the area surrounding the cap one colour, say blue. Then paint all oil cans and any containers use solely for engine oil blue. Finally paint the filler cap of the engine for the engine oil blue also. Similar arrangement can also be used for other oils e.g. yellow for gear oil and red for hydraulic oil.