Motor oil performance is communicated to consumers through standardized codes established by the American Petroleum Institute (API). These codes, often seen on the back of the bottle, ensure the oil meets specific requirements for different engines. The “SJ” designation represents a former performance level that was once the industry standard for gasoline engines.
Decoding the SJ Specification
The two-letter code “SJ” is part of the API Service Symbol. The first letter, “S,” stands for “Spark Ignition,” indicating the oil is formulated for use in gasoline-powered engines, as opposed to diesel engines. The second letter, “J,” designates the oil’s specific performance level and the standards it met at the time of its introduction.
The SJ specification was formally adopted in 1996 and mandated for use in gasoline engines starting with the 1997 model year. This oil provided improved protection against engine sludge, oxidation, and wear compared to the previous standard, SH. Oils meeting this designation were often paired with the International Lubricant Standardization and Approval Committee (ILSAC) GF-2 standard, signifying compliance with fuel economy and emission control requirements of that era.
The API Service Classification System
The API Service Classification System uses a simple alphabetical progression to denote increasing performance. The system utilizes the “S” series for spark-ignition (gasoline) engines and the “C” series for compression-ignition (diesel) engines. The second letter in the designation, starting with “A” (SA) for the most basic oils, advances alphabetically to signify a higher level of performance, protection, and additive technology.
As engine technology evolves, the API introduces a new letter designation requiring better protection against heat, deposits, and wear. The system has progressed through standards like SL, SM, SN, and the current gasoline engine standard, SP, with each new letter representing stricter performance tests. Modern oils, such as API SP, are formulated to address issues specific to contemporary engine designs, including protection against low-speed pre-ignition (LSPI) in turbocharged direct-injection engines.
Using SJ Oil Today
While the API SJ designation was the latest standard for vehicles built around 1997 through 2001, it is now considered obsolete, having been superseded by multiple generations of higher-performing oils. The current standard, API SP, offers enhanced protection for pistons, turbochargers, and timing chains compared to the SJ specification. Oils that meet the SJ standard are still technically suitable for the older engines that originally specified them.
For a consumer with a vehicle that originally called for API SJ oil, using a modern, higher-rated oil like API SP or SN is recommended. This is supported by “backward compatibility,” where newer API “S” category oils are formulated to meet or exceed the performance requirements of all previous classifications. Using a modern oil provides the older engine with superior protection against sludge and wear. Conversely, using an obsolete SJ-rated oil in a modern engine that requires a current standard like SP risks engine damage because the SJ formulation lacks the necessary additives to handle modern engine stresses.