Additives
Unlike most additives, Molybdenum is not dissolved in the base lube, but suspended as minute particles less than one micron in size. It should be noted that when Mo is used as an additive, detection of Mo to evaluate Mo-coated rings is not possible, again due to the lack of distinction between one form of a metal and another by emission spectrometric analysis. Similarly, if Zn is an additive, Zn from brass or bronze is masked. If leaded gasoline is an engines fuel, lead can not be used to evaluate potential bearing wear. We emphasize that new lubes should be tested for baseline data to avoid misinterpretation as to the source of the metal.
Typical Levels: A typical motor lube will have Mg, Ca, and or Ba from 500-3500 ppm, dependent on the specifications. (Automatic transmission fluids may have similar levels.) Lubes with high alkaline properties may have anywhere from 5000-8000 ppm Mg+Ca+Ba. Many industrial fluids have no metallic additives.
P and Zn are generally found from 600-1500 ppm. Automotive gasoline and several diesel engines usually require a minimum of 1000 ppm valve train protection, as this is the area of highest "unit" loading in such systems.
Note: ADDITIVES, with the exception of solid lubricants, are soluble in base stocks and would normally not be susceptible to filtration depletion from typical automotive filters. It is possible, however, that in the course of being consumed, an additive could form an insoluble product capable of being filtered.
The above are only a portion of the various additives developed for petroleum products, but they represent the most important ones. It should also be noted that several of the above properties can, at times, be accomplished adequately by a single additive compound.
