Engine Oils

Additives are added during the manufacturing process of engine oils.They mainly consist of metallic and polymeric dispersants,corrosion inhibitors,anti wear additives,viscosity index improvers and pour point depressants.
The basic functions of additives are:
1.To remove heat by convection cooling andas a by product would in the process reduce fuel consumption.
2.To reduce friction between engine parts by lubrication.Anti wear additives or friction modifiers such as Zinc Dithiophosphates are used to provide a thin film lubrication that shears more easily than the base metals.
This allows the engine parts to easily slide against each other .Anti wear additives , as the name suggests,reduces wear,prevents scuffing between cams and followers,rings and cylinder walls.Therefore it prevents seizing of the engine.However, they do not work well in cold coil,which is one reason starting a cold engine causes wear.The anti wear additives will eventually be consumed in time causing the oil  to degrade (oxdidize).This is the reason you must periodically change your oilsn every 5000 km for both mineral as well as semi synthetic and 10000 km for fully synthetic or 3-6 months respectively which ever comes first.Zinc that may be included in many aftermarket oil addictives doesnt give you more protection ,it just prolongs the protection if the rate of metal to metal contact is abnormally high. Adding a can of zinc rich additive will just form deposits on your valves, and may affect the spark plugs.Most good synthetic oils provide enough zinc.
3.to prevent oils from thinning too much as it warms up and also contribute to the oils ability to remain stable during extreme temperatures.Additives such as pour point depressants are added to prevent the oil from congealing at low temperatures associated with paraffin (wax) components of mineral oil crystallizing.It is not economically feasible or necessary to remove all wax from mineral oils. Pour point depressants are designed to prevent oil molecules from adhering to the wax crystals and absorbed by the wax themselves.Instead of oil attaching to the crystals and preventing flow,the oils remains separate and continues to flow.Pour point depressants are therefore said to improve flow performance at lower temperatures.
4.To suspend harmful acidic combustion by products such as unburned fuels ,sludge and carbon : additives such as metallic dispersants are used to keep dirt and debris dispersed rather than dissolving them.Ashless dispersants consists of high molecular weight whereas polymeric dispersants consists of lower molecular weight additives for situations in which viscosity index improvers are not necessary.Ashless dispersants are more effective than metallic dispersants in controlling sludge and varnish deposits that form during intermittent or low temperature operations.
5.To reduce corrosion up to a reasonable time additives such as oxidation/rust inhibitors are used to neutralize acids (varnish,sludge,contamination by water and corrosive organic compounds) by forming a protective film on bearing surfaces which makes the surface impervious to acidic effect.Compounds such as Alkaline Phenate and Sulfonate prevent corrosion wear from blow by gases that have forced past the rings during combustion.This contains incomplete products of combustion or from oxidation of the base lubricant that by itself produce acids that will react with the oxides of the bearing materials and corrode them.Nitrogen based acids,water and organic peroxides still make anti corrosion additives an important part of modern engine oils.

Aftermarket Additives

It is said that the respective additive compounds that are already added during manufacturing of engine oils performs a specific task vital to the life span and performance of an engine.A right blend of additives is necessary because too much of any one additive can upset the balance and render unpredictable performance.The aftermarket additives may come into conflict with the oil's existing additives by cancelling out each other as they compete for the same lubricating surface.Moreover,any additional additives added must maintain compatibility with other system materials in order to preserve gaskets,rubber,plastic or vinyl seats,clutch plates and other metallic components of the system.

Most engine manufacturers do not recommend oil supplement of any kind.Good quality synthetics offer all the protection necessary if one follows the oil change schedule religiously.Be also informed that extra additives cannot revitalize worn oil as many have mistakenly believe.PTFE(polytetraflouroethylene)aka Teflon is not useful as an ingredient in oil additives.They may actually block the oil filter and the oil ways of your engine.Your engine wear may significantly increase as metals found in the oil,cylinder walls,oistons,camshafts,and lifters don't stay in suspension.In the final installment we would be concluding with the function of oil filters and why synthetics are better than mineral oils.