Additives
Detergents, as the name implies, help maintain engine cleanliness by preventing deposits on critical areas such as ring lands, or by removing such deposits. They also help maintain deposits such as fuel, soot in suspension to be filtered out or drained with the lube. Metallic carriers are generally used (except where ''ash-less'' lubes are required) to bring the non-metallic portion, which is the "detergent" part of the compound, to the lube. The metal, however, is also beneficial in itself for it is alkaline, acting as a neutralizer for corrosive acids, thus helping to give the lube its Total Base Number.
Detergent Carriers: Ca, Mg, and Ba, in order of current use frequency, are the most common metals used as carriers. Typically only one of these three metals is found in a specific brand and type of motor lube, dependent on how the supplier chooses to meet the desired specification. It is possible, however, to find new lubes using a combination of metals to achieve the same purpose. There is no rule.
These metals impart alkaline properties to the lubricant, enabling it to neutralize corrosive acid. Mg has the highest alkalinity given weigh amount while Ba has the least For this reason Mg and Ca are nearly exclusively found in high performance motor lubes with sulfated ash limitations (such as lubes for Detroit Diesel engines).
Dispersants: Dispersants have overlapping properties with detergents, in that they, too, maintain particles in suspension. Many technical people distinguish the two terms by calling metallic particle suspenders detergents and totally nonmetallic (ash less particle suspenders) dispersants. They reduce the tendency of small particles to combine into larger particles, taking some of the burden off the filters, and prevent deposit of these particles on valve covers and moving parts, particularly at low temperatures. PALs solids test aids in monitoring the effectiveness of the lubes dispersants.
Defoamants: This material acts in a very complex chemical and physical manner to minimize foaming tendencies of lubes. It has limited solubility in lubricants of a non silicon nature, and this limited solubility helps effectiveness in accelerating the formation of large bubbles from small ones which dissipate from lube much more readily. The larger bubbles rise to the surface quickly and then break.
The most common defoamant in use is a silicon polymer. It is usually added at the low ppm level; thus, it is not unusual see up to 12 ppm silicon in new lubes, although 3-7 ppm is a typical range. Testing the new lube is important, for additional silicon from the starting level will usually indicate abrasives (dirt).
