LO 10-2 Describe the purpose, properties, function, composition, types, and applications of diesel engine lubricating oils

1.11. The American Petroleum Institute Certification Mark for Diesels

The American Petroleum Institute Certification Mark for Diesels

Intended for 2017 and later diesel engines to help meet GHG emissions targets, oils that are tested for and meet the API CK-4 specifications are permitted to carry the certification mark. CK-4 was introduced in the 2017 model year for GHG engines using exhaust gas recirculation (EGR), diesel particulate filters (DPF), and selective catalytic reduction (SCR) systems. The PLUS-4 suffix (e.g., CI-4 and CJ-4) indicates that the oil provides a higher level of protection against changes to viscosity related to soot loading and viscosity loss due to oil molecule shear in diesel engines. This 2017-PLUS oil standard is built on the CJ-4 specification for compatibility with diesel engine applications burning ultra-low–sulfur diesel (ULSD) fuel and with the intent to prevent poisoning as well as the plugging of the exhaust catalyst. Because combustion blowby products entering the oil around the rings is different in engines burning ULSD and using EGR, these oils must be capable of holding more soot while neutralizing less acidic oil than engines burning fuel with more sulfur. Starting in 2007, because oil consumed in the cylinders ends up in the particulate filter where oil additives leave ash residue that must be physically cleaned out of the particulate filter, CJ-4 oils were formulated to produce minimal ash residue that could block exhaust gas flow through the DPF. This ash cannot be removed by regeneration. When the DPF is loaded with ash, the filter requires removal and cleaning. The primary differences between CJ-4 and the latest CK-4 are GHG-reducing technologies that require engines to run hotter and consume less fuel. By lowering internal engine friction and energy losses caused by pumping oil, the new oil contributes to the fuel savings. There are several advantages to using the CK-4 oil:

• Improved shear stability: It will not lose its viscosity as quickly due to cutting of oil and viscosity improver molecules when compared to earlier oils.
• Improved oxidation resistance: Oil can combine with oxygen when hot and begin to thicken.
• Aeration resistance: Small air bubbles will not remain dissolved in the oil as easily compared to earlier oils.
• Improved resistance to scuffing: Improved anti-wear additives will lubricate metal surfaces when inadequate oil film is momentarily missing.