Are BS6 Diesel Engine Oils backward compatible with BS4 Engines as well

Many Auto manufacturers have slimmed down the Diesel Vehicle line up in the passenger car segment with BS6 Emission norms coming in, sighting the high production cost. However, the commercial vehicle industry still mainly complies with Diesel Engines maximizing the power output. While many commercial vehicle OEM’s have initiated CNG as an alternative fuel for small and medium vehicles the dependency on Diesel engines yet remains strong.

Knowing CK-4 Diesel Engine Oil and its application: 

 
The new oil standard was developed to better protect new generation as well  older engines (BS4 & BS3) improve engine oil performance, and help engine manufacturers meet 2020 government emissions standards of BS6. 

API Service Category CK-4 describes oils for use in high-speed diesel engines designed to meet 2020 model year complying emission standards on-highway and  for previous model  diesel engines. 

API CK-4 oils are designed to provide enhanced protection against oil oxidation, viscosity loss due to shear, and oil aeration as well as protection against catalyst poisoning, particulate filter blocking, engine wear, piston deposits, degradation of low- and high-temperature properties, and soot-related viscosity increase. 

These oils are formulated for use in all applications with diesel fuels ranging in sulphur content up to 500 ppm (0.05% by weight). However, the use of these oils with greater than 15 ppm (0.0015% by weight) sulphur fuel may impact exhaust aftertreatment system durability and/or oil drain interval.

These oils are especially effective at sustaining emission control system durability where particulate filters and other advanced aftertreatment systems are used (DPF, SCR etc.)

Can API CK-4 Diesel Engine Oils be applicable for older Engines?

API CK-4 oils exceed the performance criteria of API CJ-4, CI-4 with CI-4 PLUS, CI-4, and CH-4 and can effectively lubricate engines calling for those API Service Categories. 

Benefits of API CK-4:

API CK-4 diesel engine oils are low SAPS (Sulphated Ash, Phosphorus and Sulphur) diesel engine oils and the most suitable lubrication solution for new engines fitted with after treatment devices (ATD). Since commercial vehicles are largely run on diesel. To achieve stringent emission norms these vehicle are fitted with exhaust after treatment devices. 

These exhaust after-treatment devices help in meeting the stringent limits of NOx and PM by converting them chemically into less harmful exhaust gases and by filtering out the harmful particulates. Diesel engines produce soot due to incomplete combustion of diesel fuel in the engine’s combustion chamber. To meet the stringent limits of BS VI emission norms for Particulate Matter (PM), diesel particulate filters (DPF) are fitted to the vehicle to filter out these soot particulates. As soot gets collected in the DPF, it gradually gets burned off, however, not completely. A proportion of these soot particles is comprised of unburned oil. These oil particles contain substances (such as some engine oil additives) which cannot be completely burned away and are therefore deposited as ash in the DPF. The ash can only be removed by physically cleaning the DPF.

Conventional diesel engine oils such as API CF-4, API CH-4, API CI-4 and even API CI-4 PLUS produce higher levels of ash and hence will not be suitable for or compatible with diesel vehicles, whether passenger or commercial, fitted with DPF and other ATD.