Here is some stuff I have had in my Documents folder for some time and thought it might be of interest for the newbies on here. Classification Systems Oil is classified according to two systems. One system determines the oil’s viscosity (the SAE grade), and one system determines its performance level, i.e. which to use in what type of engine(API class). I. SAE Grade The Society of Automotive Engineers (SAE) Viscosity Grade is a system based on viscosity measures taken from a variety of tests. This system established eleven distinct motor oil viscosity classifications or grades: SAE0W,SAE5W,SAE10W,SAE15W,SAE20W,SAE25W,SAE20,SAE30,SAE40,SAE50,and SAE60. These are known as single grade or viscosity oils. These grades correspond to specific ranges that the particular oil falls into. The “W” in the classification indicates that the grade is suitable for use in cold temperatures. (You can think of the “W” as standing for “Winter”.) The classifications increase numerically, allowing you to tell the difference between them and what this difference means. In simple terms, the lower the number, the lower the temperature at which the oil can be used for safe and effective protection. The higher the number, the better protection offered for high heat and load situations. Single grade oils have a limited range of protection and so have a limited number of uses. In order to increase an oil’s usefulness, it must be able to meet the requirements of two or more classifications. Multi-grade or multi-viscosity oils effectively meet the viscosity requirements of two or more classifications. Examples of multi-viscosity oils are SAE0W-30,SAE5W-30,SAE10W-30,SAE15W-40 and SAE20W-50. The number with a “W” focuses on an oil’s properties at low temperatures. The number without a “W” characterizes properties at high temperatures. A multi-viscosity or multi-grade oil, e.g. 10W-30, meets the 10W criteria when cold and 30 criteria once hot. SAE10W-30 and SAE10W-40 are widely used because under all but extremely hot or cold conditions, they are light enough for easy engine cranking at lower temperatures, and heavy enough to protect satisfactorily at high temperatures. II.API Class The American Petroleum Institute (API) developed a classification system to identify oils formulated to meet the operating requirements of various engines. The API system has two general categories: S-series and C-series. The S-series service classification emphasizes oil properties critical to gasoline or propane fueled engines. The “S” stands for spark-ignited engine and the “C” stands for compression-ignited engine. If an oil passes a series of tests in specific engines (API Sequence tests), the oil can be sold bearing the applicable API service classification. There are nine different S-series classifications:SA,SB,SC,SD,SE,SF,SG,SH,and,SJ. The S-series classifications progress alphabetically as the level of lubricant performance increases. Each classification replaces those before it, with SJ currently offering the most protection. SJ oil may be used in any engine, unless the engine manufacturer specifies “non-detergent” oil. SA and SB are non-detergent oils and are not recommended for use unless specified. SC oils were required for new car warranties from 1964 to 1967. SD oils were required from 1968 to 1970 and a few in 1971. Some new car warranties required SE oils in 1971 and its use continued through 1979. New car warranties from 1980 to 1989 require SF oils. The API approved specifications for the SG classification in March of 1988. SG addresses problems with deposit buildup, changing fuel compositions, and new designs for smaller, hotter and leaner burning engines. New car warranties after 1989 require the use of oil meeting the SG classification. 1994 models required SH and in 1997 SJ became the latest. SJ features a drop in phosphorus levels. Zinc dialkyldithiophosphate commonly called ZDDP has been used as an engine oil additive since the 1940’s, and it is the phosphorus from ZDDP that poisons catalytic converters. C-Series classifications deal with diesel engines. There are ten classifications: CA,CB,CC,CD,CD-II,CE,CF-4,CF,CF-2,CG-4. CA and CB are non-detergent oils and are no longer used. The CC classification was designed for use in naturally aspirated or lightly turbocharged diesel engines operating under light to moderate duty conditions and running on low sulfur fuel. The CD classification is designed for use in turbocharged and supercharged diesel engines operating under moderate to heavy duty and running on fuels of various qualities. The CD-II classification was developed to meet the specific needs of the Detroit Diesel Allison (DDA) two-stroke or two-cycle diesel engines. It is usually a single viscosity oil with additives designed to combat the effects of high sulfur fuel content. The CE classification was designed for use in turbocharged or supercharged heavy duty diesel engines manufactured since 1987. These classifications have been replaced in 1994 with CF, and CF-2. CG-4 was also introduced in 1994 for the severe duty diesel engines, replacing CF-4. Unlike the S-series classifications, the C-series classifications do not necessarily supersede one another. The C-series classifications have specific applications. Generally, CF, and CF-2 applies to automotive and light truck diesel engines; CG-4 for heavy duty diesel engines. Follow recommended API service classifications from the engine manufacturer. The SAE and API classification systems are intended to help motorists choose the right oil for their needs. The choice depends on the engine, the outdoor temperature and the type of driving the motorist does most. Most motorists are more familiar with the SAE Viscosity Grade system than they are with the API Class system. They buy a lower SAE grade such as 5W-30, for cold weather and a higher SAE grade, such as 10W-40, for hot weather. However with the wider operating range of the synthetic oils one grade can be used for all seasons. SJ is the current API class. SJ oils are widely available and most gasoline engine automobiles either specify SJ oil or, if they were manufactured before the SJ class was created, may use SJ oil. However, one should be sure to purchase SJ class oil for the best engine protection available. Of course, motorists should follow the oil specification of their vehicle owner manual.