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There are a number of different after-market oil additives which are advertised as “enhancements” to motor oils currently in service. These additives may consist of a concentrated anti-wear additive, a viscosity improper only, solid lubricants suspended in oil, solvent, or straight mineral oil. The list goes on and on. We are often asked whether these products are compatible with our various motor oils or not.

Pennzoil does not recommend the addition of any motor oil additive to any of its products. Although some of the oil additives available may be beneficial in an inferior quality motor oil, they are not recommended for addition to high quality, fully formulated motor oils, such as the ones Pennzoil produces. There exists a delicate blend of an optimum level of chemical additives in specific base oils which can be upset by the addition of other materials. The concept of “the more additive, the better the oil” does not hold true. There are some additives that may provide a maximum level of protection at a specific concentration, and exceeding that concentration actually decreases performance capabilities.

The effects of some of the various types of after-market oil additives are discussed in general terms as

  • Additives containing primarily solvents are intended to clean up engine deposits but can contribute significantly to dilution of the oil viscosity and may even loosen harmless deposits in isolated areas of the engine and deposit them in other areas which may be harmful.
  • Additives that contain very light mineral oil are also intended to have a solvency effect in the engine, but generally, do little more than dilute the viscosity of the motor oil in use.
  • The addition of additives containing solid lubricants, such as molybdenum disulfide, graphite, copper powder, etc., usually results in the separation of the solid materials to the bottom of the oil sump. Although these materials may have excellent friction-reducing properties in many applications, they are very difficult to keep suspended in the oil, and if the original oil was not formulated to suspend them they will normally settle out of the oil, plug oil passages, bearing holes, etc. and lead to engine failure.
  • Additives which consist primarily of viscosity index improvers are generally very thick and viscous and can not be expected to mix thoroughly with an oil that is already present in an engine. These additives may help to temporarily thicken an oil and quiet noisy lifters, however, depending upon the quality of the viscosity improver, the effect may only be temporary. Over-treat of these types of additives can result in oil that is too thick to properly lubricate.
  • The addition of additives which are concentrated extreme pressure or anti-wear agents may result in actual metal attach by these very potent materials.

It is impossible to discuss each and every type of motor oil additive available and what effects they may have. The important point to retain in general is that these materials are not recommended for addition to Pennzoil Products.