Why is it so important to use detergents and dispersants in diesel engine oil?

Quite simply detergents and dispersants in diesel engine oil are vital in controlling the combustion by-products which find their way into the crankcase.

Diesel fuel combustion (or incomplete combustion) is accompanied by the production of soot (unburned carbon). Prior to exhaust emissions legislation this soot simply passed into the atmosphere through the exhaust system.

Soot reduction has been accomplished by improving injector spray patterns,
combustion chamber design (reentrant bowls), diesel fuel refining (minimizes unburnable heavy materials), and retarding fuel injection timing. Retarded fuel injection timing serves to burn soot by keeping the exhaust manifolds hot, thereby allowing more time to complete the combustion process as the unburned carbon passes through the heated exhaust system.

Detergents and dispersants in diesel engine oil control soot.

Engine OEMs and oil additive manufacturers have developed lubricants with detergents and dispersants in diesel engine oil that can suspend greater volumes of soot (as much as 10% volume) in the lube rather than depositing it on engine components where it could cause premature engine failures.

This is primarily accomplished by adding more detergents to the oil to better neutralize acidic byproducts of combustion, while adding more dispersants to suspend soot particles in the oil. Current diesel engine oils contain about twice as much detergent and dispersant as petrol motor oils.

From the advent of American Petroleum Institute (API) CD oils in the ’60s to API CI-4 Plus oils in the early 2000s, detergents and dispersants in diesel engine oil have increased significantly to improve diesel oil performance and lengthen oil change intervals.

Environmental laws set in 2007 forced emissions levels so low that catalytic converters and particulate traps are now required to pass exhaust emissions tests.

API CJ-4 oils have tighter specs regarding detergents and dispersants in diesel engine oil.

Engine builders, additive manufacturers and oil marketers teamed up to develop API CJ-4 oils for these engines. CJ-4 oils have reduced ZDDP levels to minimize phosphorus “poisoning” of catalytic converters and particulate traps. Whilst exhaust sulfate emissions (remember, sulfates plus water equal sulfuric acid) were also reduced by controlling the detergents and dispersants in diesel engine oil.

 With diesel engines becoming more complex it’s vital that you only use quality lubricants and Habot Synthetic Lubricants have the best synthetic lubricants with detergents and dispersants in diesel engine oil that have been tried and tested.