Service DS. “Service typical of diesel engines operating under extremely severe conditions or having design characteristics or using fuel tending to produce abnormal wear or deposits.” The DS service is summarized as:
1. Extremely severe
2. Definite special lubrication problems to control
3. Some design characteristics adversely influencing wear and deposits
4. Some adversely low or adversely high engine-operating-temperature conditions
5. Adverse fuel, high in sulfur content
Markings on Containers. Oil manufacturers are to indicate the service or services of an oil, for service ML, for service MM and so forth. The container will be labeled as shown in Fig. 5–3. If an oil is suitable for more than one service, it may have a multiple designation as, “For Services MS—DG.” This designation means that such an oil is satisfactory for the most severe gasoline-engine service and also for the still different requirements of general diesel-engine service.
FIG. 5–3. Marking for oil container showing type of service. (Standard Oil Company.)
Grades of Engine Oils. The Society of Automotive Engineers grades engine oils according to their body or viscosity as SAE5W, SAE10W, SAE20-20W, SAE30, SAE40, and SAE50 (Table 5–1). The W after the number indicates that the oil is suitable for winter use. The 20–20W is an oil suitable for both summer and winter use.
TABLE 5–1. SAE CRANKCASE OIL CLASSIFICATION (Adopted Oct. 3, 1950)
Note A. Minimum viscosity at 0°F. can be waived provided viscosity at 210°F. is not below 40 seconds Saybolt Universal.
Note B. Minimum viscosity at 0°F. can be waived provided viscosity at 210°F. is not below 45 seconds Saybolt Universal.
No oil in any of the new SAE grades may have a viscosity less than 39 seconds Saybolt Universal at 210°F. This minimum limitation applies to the W oils as well as to the others, but naturally is of particular significance in the case of the extremely light grades.
GEAR LUBRICANTS
Gear Lubricants. The American Petroleum Institute gives three definitions of gear lubricants, as follows:
1. Regular-type gear lubricant. “This term designates gear lubricants generally suitable for use in automotive transmission and in most spiral-bevel and worm-gear differentials.”
2. Worm-type gear lubricant. “This term designates gear lubricants generally suitable for use in truck-type worm-gear axles under severe conditions of service.”
3. Mild-type E.P. (extreme pressure) gear lubricant. “This term designates gear lubricants having load-carrying properties suitable for many automotive transmissions and spiral-bevel differentials under severe conditions of speed and load.”
The SAE viscosity grade for gear lubricants is given in Table 5–2.
In general, SAE 140 is recommended for high-temperature summer operation, SAE 90 for moderate-temperature conditions, and SAE 80 for use under severe low-temperature conditions. Manufacturers of tractors and equipment usually recommend the grade of lubricant to use for any particular gear-drive mechanism.
Viscosity. The viscosity of an oil is a measure of its fluidity or flow-ability at definite temperatures. The viscosity is usually determined at temperatures of 100 and 210°F. An oil to be tested is placed in a viscosimeter or the Saybolt apparatus, consisting of a specially shaped vessel equipped with a standard size orifice, or opening, at the lower end. This vessel is surrounded by a liquid bath for temperature control. Thermometers are placed in both the oil and the bath liquid. The orifice is kept closed with a cork until the two liquids have been heated to 100 or 210°F. The cork is removed and the oil permitted to flow into a graduated flask. The time, expressed in seconds, required for 60 cubic centimeters of oil to flow through the orifice is called the viscosity of the oil at the temperature tested. The viscosity at other temperatures can be calculated. A special viscosity-index chart has been worked up for the chemist. The effect of viscosity on lubricating a bearing is shown in Fig. 5–4.
TABLE 5–2. SAE CLASSIFICATION OF GEAR LUBRICANTS
* Lubricant manufacturer responsible for maintaining satisfactory minimum.
† Lubricant manufacturer responsible for maintaining satisfactory maximum.
FIG. 5–4. Effects of viscosity in lubricating a bearing. (John Deere.)
GREASES
The American Society for Testing Materials defines a petroleum lubri eating grease as “a semisolid or solid combination of a petroleum produc and a soap, or a mixture of soaps, with or without fillers, suitable fo certain types of lubrication.” In ancient times a grease made of anima fat was probably used to lubricate the axles of chariots. Mineral oil grease was developed soon after the discovery of oil in 1859. Early farm ma chinery which was drawn by horses had few moving parts and almost an type of grease would suffice to reduce friction. Modern power-operated machinery has many bearings carrying light to heavy loads. Some parts operate at high speeds and high temperatures and require special high quality greases. A water-repellent grease is required for water pumps; a soda-base grease of spongy or fibrous texture, for wheel bearings and universal joints; a cup grease, for distributor shafts; and a soft tacky grease for chassis joints.
FIG. 5–5. Hydraulic hand-push grease gun and fittings, showing cross section of nozzle and fitting. (Alemite Division, Stewart-Warner Corp.)
Classes of Greases. Greases as indicated above are classed according to the use and application for which they are specially suited. There are many types, but the most common are (1) chassis greases, (2) wheel-bearing greases, (3) water-pump greases, (4) universal-joint greases, and (5) the cup greases. The greases used most are the chassis and the wheel-bearing greases. The chassis grease is designed for pressure-gun application, while the wheel-bearing grease is generally packed in the whee bearing by hand.
FIG. 5–6. Lever-type grease gun.
FIG. 5–7. Portable hand-tank grease guns and pails: A, interchangeable pail pump with hose; B, installing pail pump on pail; C, interchangeable pail pump for gear oils; D, interchangeable pail hand-gun loader; E, detachable lid for hand-gun loader; F, portable grease