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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.

Major oil companies do 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 motor oils. 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 which may provide a maximum level of protection at a specific concentration, and exceeding that concentration they actually decrease performance capabilities.

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

• 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 which contain a very light mineral oil are also intended to have a solvency affect in the engine, but generally do little more than dilute the viscosity of the motor oil in use.

• Addition of additives containing solid lubricants, such as molybdenum disulfide, graphite, copper power, etc., usually results in 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, holes, etc. and lead to engine failure.

• Additives which consist primarily of viscosity index improvers are generally very thick and viscous and cannot be expected to mix thoroughly with an oil that is already present in an engine. These additives may help to temporarily thicken an oil an

d quiet noisy lifters, however, depending upon the quality of the viscosity improver, the effect may only be temporary. Over treat with any of these type of additives can result in an oil which is too thick to properly lubricate.