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Oil Additives For Diesel Engines- Are They Worth It?

Posted by: Erik Bjornstad

The finished engine oil you buy isn’t just base petroleum oil pulled out of the ground. It’s an engineered combination of refined oil base stocks and a package of different additive components that have been blended in order to make the engine oil function better in important ways.  That’s the biggest difference between the oils of today vs. yesteryear – we have better additive packages that make today’s oils more effective and better suited to protecting today’s high performance diesel engines.

oil-additives-for-diesel-engines.jpgEngine Oils Already Come With Additives

Today’s finished diesel engine oils will contain important additive components to help with:

Viscosity modifiers – these are added to help the oil maintain its viscosity properties in hot and cold weather. These viscosity modifier additives are what enabled the industry to come up with multiweight oils that have different viscosity ratings in hot weather and cold weather.

Corrosion and rust inhibitors – these are polar constituents that attract to the metal surfaces in the engine and form a protective film to guard against corrosion.

Detergents – these are essential to keeping metal surfaces free from deposits that form in the engine environment. Typically they will react with any sludge or varnish that has formed and make them soluble so that they can be drawn up into the oil film and away from the metal surface where they can otherwise cause damage.

Dispersants – these are essential, too, for keeping those metal surfaces free from the kind of contaminants (like soot) which can damage them. A dispersant will attract to the contaminant molecule and draw them up (disperse them) into suspension in the oil film.

Today’s diesel engine oils also have an API Service Category associated with them. The most current service category for diesel oils is CJ-4. This designation gives you the assurance that your diesel oil meets the most current and necessary specifications to show that it will adequately protect your diesel engine.

What about diesel oil additives? What value do they have?

Like fuel additives, there are good ones and bad ones to choose from. But given that diesel engine oils already contain the most important kinds of additives, do you even need an oil additive? Some of them can add significant value.

But it’s important to have proper perspective on what you think it’s going to do.  Since the oil already contains the most essential additive ingredients, the best diesel engine oil additives can provide value by supplementing what’s already in there.  There’s value in this because these additives get used up over time. The dispersants and acid neutralizers and detergents get used up as they perform their essential functions. So adding a diesel engine oil additive can provide value by extending the period through which these essential additives last. 

A good oil additive can also enhance the oil’s extreme pressure characteristics (its EP properties) by adding some kind of constituent that improves the oil’s ability to provide lubrication under extreme pressure.  However, don’t buy into the idea that oil is completely lacking in this regard. All oils have some level of EP additive already in them, usually ZDPP.  An oil additive can supplement this (depending on what it is, of course).

So what you don’t need is an oil additive that makes claims that engine oil just doesn’t contain a specific kind of essential component that, through its absence, is going to destroy your engine (unless you buy their additive, of course). That’s severe overmarketing.  Reputable oil additives of high quality that do what they claim will not need to oversell themselves.

You may be interested in these related posts:

Which Oil Additive works the best? Oil Additives Test

How to Choose the Best Diesel Fuel Additive for You

This post was published on December 20, 2016 and was updated on December 20, 2016.

Topics: Lubrication, Diesel, Heavy Trucks and Equipment