CJ-4 Answers

Answers about CJ-4 engine oil.


API CJ-4 is the latest diesel engine oil specification designed to cover the lubrication requirements of new, heavy duty engines that comply with the U.S. Environmental Protection Agency's (EPA) 2007 on-highway truck exhaust emissions regulations.

API CJ-4, known as PC-10 (proposed category) during its developmental stage, will be licensable on October 15, 2007. The major engine builders will likely put out their 2007 low emission engines starting in the fourth quarter of 2006. Most engine builders will use enhanced exhaust gas recirculation (EGR) and exhaust after-treatment devices such as diesel particulate filters to attain the stringent NOx and diesel particulate emissions standards. Keeping in line with this change, ultra low sulfur diesel (ULSD) fuel containing less than 15 ppm (parts per million) sulfur, will become commercially available for on-highway use starting the third quarter of 2006. Use of ULSD in the new engines is critical in meeting the new exhaust emissions standard. In addition, API CJ-4 quality oils containing reduced ash, phosphorus and sulfur are required to ensure the performance and life of exhaust after-treatment devices.

The CJ-4 oils are somewhat different from those of the previous categories such as CI-4, due to the chemical limits of this specification. To safeguard the effectiveness and life of the aftertreatment devices, the new oils are lowered in sulfated ash, phosphorus and sulfur (SAPS). Further, the new engines will be equipped with closed crankcase ventilation (CCV) to control evaporative emissions, and to maintain the effectiveness of the CCV system the volatility of the oil will be reduced. As a result, the CJ-4 category oils will be subject to the following limits:

  • Sulfated Ash—1.0 wt%
  • Phosphorus—0.12 wt%
  • Sulfur—0.4 wt%
  • NOACK Volatility—13 wt% (SAE 15W40)

Familiarity with the term "low SAPS" technology is important. The low SAPS technology results in API CJ-4 oils of 8.5 to 9.5 TBN. That is a big change for someone accustomed to 10 to 12 TBN and higher for the API CI-4 and CI-4 PLUS class of oils. The TBN is generally derived from the ash containing detergent additives. Whereas the CI-4 oils typically range in sulfated ash from 1.1 to 1.5 percent, the CJ-4 oils are limited to a maximum of 1.0 percent sulfated ash.

The diesel engines meeting the new emissions standard are predicted to run hotter and possibly cause more soot in the oil. Because of this, the CJ-4 oils are formulated for better oxidation stability, increased soot control and higher wear protection. Obtaining enhanced performance at reduced SAPS is a challenge. Consequently, the CJ-4 oils are supplemented with non-ash and non-phosphorus containing additives to bolster performance and withstand the harsher operating environment of the new 2007 engines.

The API CJ-4 oils are backward compatible for protection of pre-'07 engines that specify service under previous categories such as API CI-4 PLUS or CI-4. The CJ-4 oils are formulated from superior technology that has been developed to meet performance requirements of the 2007 low emission engines without compromising the performance in older engines. As a part of API CJ-4 qualification program, the new oils will have been tested to demonstrate performance at the API CI-4 or CI-4 PLUS level as well. The CJ-4 oils are optimized for use in equipment using diesel fuel containing up to 500 ppm sulfur. But, it should be noted that use of ULSD is required in the 2007 low emissions engines equipped with after-treatment devices.

As always, customers should consult the engine manufacturer or owner's manual for engine service and oil drain interval recommendation. Whereas the quality of the lubricant generally has an impact, it is not the only factor that determines the specific service interval for any engine. The service intervals vary depending on type of equipment, type of service, load factors, environmental factors, operational severity, fuel, etc.

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