Nearly all lubricants contain engine oil-additives whether the oils are synthetic or petroleum based.

Engine oil-additives are chemical compounds that improve the lubricant performance of base oil.

Engine oil-additives have three basic roles:

  1. Enhance existing base oil properties with antioxidants, corrosion inhibitors, anti-foam agents and demulsifying agents.
  2. Suppress undesirable base oil properties with pour-point depressants and viscosity index (VI) improvers.
  3. Impart new properties to base oils with extreme pressure (EP) additives, detergents, metal deactivators and tackiness agents.

Engine Oil-Additives
Engine Oil-Additives

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Most of these engine oil-additives will already be in the oil as it comes from the manufacturer. Yet if you walk into an auto supply store, you’ll find bottles of aftermarket engine oil additives. Many claim to improve performance even further and make your engine cleaner than the detergents already in your oil. Are these additives worth buying? Will they do a better job than the additives already in your oil? Or are they just redundant and possibly even harmful?

This is a subject of some controversy, but on the whole they probably won’t make much difference.

Most oil will include the given base oil as well as various additives like;

  • Antacids
  • Dispersants
  • Detergents
  • Viscosity and friction modifiers

The particular blend of a given oil will be equipped to meet the lowest recommended needs of the engine. This does leave room for improvement, however.

In order to be beneficial, oil additives must mix well with these oils. For instance, most engine oil includes detergents to keep the metal surfaces clean and wick away contaminants. Adding a dispersant to the oil can aid in this job by pulling dirt or soot away from the metal.


ZDDP-Zinc dialkyldithiophosphate

Is a zinc and phosphorus compound that until recently, formed a component of anti-wear additives. However, because of its propensity to damage the catalyst in converters, fewer oils now contain it. Even so, older vehicles that have a flat-tappet camshaft need special motor oils that include this compound. The ZDDP provides the necessary lubrication to the cam lobes, lifter bodies, lifter bores and other engine parts.