Читать книгу Farm Machinery and Equipment - Harris Pearson Smith - Страница 25

Prior to 1952, automotive types of engine oils were classed as regular, premium, and heavy-duty. The American Petroleum Institute has set up a new system of service classification, designations, and definitions for automotive types of engine lubricating oils. The three basic factors involved are:

1. The type of engine

2. The kind of service

3. The nature of the fuel

The two basic engine types are the gasoline or other spark-ignition engines and the diesel engines. Oils for the gasoline and spark-ignition engines are given the designation of M, while the oils for the diesels are designated as D oils.

FIG. 5–2. Diagram showing refining process and the points where the oils and greases are obtained. (Standard Oil Company.)

Three kinds of service are set up for the gasoline or other spark engines. These are:

1. Service ML—light and favorable

2. Service MM—moderate to severe

3. Service MS—unfavorable or severe

The American Petroleum Institute (API) defines and explains the three classes of services as follows:

Service ML. “Service typical of gasoline or other spark-ignition engines operating under light and favorable service conditions, the engines having no special lubricating requirements and having no design characteristics sensitive to deposit formation.” Thus, ML service can be summarized as:

1. Light and favorable conditions

2. No special lubrication problems to control

3. No design characteristics sensitive to deposit formation

4. Mostly moderate-speed driving

5. No severe low-temperature or high-temperature service

Service MM. “Service typical of gasoline and other spark-ignition engines operating under moderate to severe service conditions, but presenting problems of deposit or bearing corrosion control when crankcase oil temperatures are high.” The MM service is summarized as:

1. Moderate to severe conditions

2. Some high-temperature problems of deposit or bearing corrosion to control

3. No design characteristics sensitive to deposit formation

4. Fuel of suitable characteristics

5. No severe low-temperature service or prolonged idling

Service MS. “Service typical of gasoline or other spark-ignition engines operating under unfavorable or severe types of service conditions, and where there are special lubrication requirements for deposit or bearing corrosion control, due to operating conditions or to fuel or to engine design characteristics.”

Under the MS service, there are two types of severe service or operating conditions, namely, (1) start-and-stop service and (2) high-temperature service. The MS service is summarized as:

1. Unfavorable or severe conditions

2. The most severe service encountered

3. Definite special lubrication problems to control

4. Low-temperature severe service

a. Much stop and go

b. Much idling

c. Much crankcase condensation

d. Much unburned fuel

5. High-temperature severe service

a. Prolonged high speeds

b. Inadequate cooling

c. Adverse fuel impurities

Diesel Engine Services. Service DG—“Service typical of diesel engines in any operation where there are no exceptionally severe requirements for wear or deposit control due to fuel or engine design characteristics.” The DG service is summarized as:

1. General or moderate

2. No exceptionally severe lubrication problems to control

3. No design characteristics adversely influencing wear and deposits

4. No adversely low or adversely high engine-operating-temperature conditions

5. No adverse high-sulfur-content fuel

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.