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American Petroleum Institute
A Guide to the API Engine Oil Licensing and Certification System
Performance
Levels
(continued)
CH-4 - To be introduced in the API Service Symbol on December 1, 1998, CH-4 oils are suitable for high-speed, four-stroke diesel engines designed to meet 1998 exhaust emission standards and are specifically compounded for use with diesel fuels ranging in sulfur content up to 0.5% weight. CH-4 oils are superior in performance to those meeting API CF-4 and API CG-4 and can effectively lubricate engines calling for those API Service Categories.
CF - CF oils are suitable for off-road, indirect-injected diesel engines and other diesel engines using fuel with higher sulfur content, typically over 0.5% weight. Oils meeting this category were introduced in 1994 and can be used in engines requiring CD oils.
CF-2 - CF-2 oils are suitable for severe-duty, two-stroke-cycle diesel engines. Oils meeting this category were introduced in 1994 and can be used in engines requiring CD-II oils.
CF-4 - CF-4 oils are suitable for high-speed, four-stroke, naturally aspirated and turbocharged diesel engines.
CG-4 - CG-4 oils are suitable for severe-duty, high-speed, four-stroke diesel engines used in highway and off-road applications where fuel sulfur content is less than 0.5% weight. Oils meeting this category are required for engines meeting 1994 emission standards. They can be used in engines requiring CF-4 oils and previous categories.
For reference, all of the service categories that were ever issued are listed in this guide under API Service Categories. Any of the service categories may be used on the container outside of the API Service Symbol to indicate the performance qualities of the oil. However, only those currently licensed (see above) by API can appear inside the API Service Symbol. Keep in mind two facts about a service category designation that appears outside of the API Service Symbol: (1) by law, the actual contents of the container must meet all the specifications claimed for it; and (2) the marketer may not have certified to API that the oil meets these specifications.
SAE
Viscosity
Grade
The center of the API Service Symbol shows the oil's SAE viscosity grade. Viscosity is a measure of an oil's flow characteristics, or thickness, at certain temperatures.
The low-temperature viscosity (the first number, 5W or 10W, in the examples to the left) indicates how quickly an engine will crank in winter and how well the oil will flow to lubricate critical engine parts at low temperature. The lower the number the more easily the engine will start in cold weather.
The high-temperature viscosity (the second number, 30, in the examples to the left) provides thickness, or body, for good lubrication at operating temperatures.
A multigrade oil (for example, SAE 5W-30) provides good flow capability for cold weather but still retains thickness for high-temperature lubrication.
A single grade oil (a single number in the center of the API Service Symbol) is recommended for use under a much narrower set of temperature conditions than multigrade oils.
Operators should refer to their owners' manuals to select the proper viscosity oil for the ambient temperature and operating conditions at which the equipment will be used.
© 1995-2000, American Petroleum Institute
