Car Engine Oil Additives Packages Explained
Engine oil consists of about 80% base stock, the rest is additives.
What's meant by car engine oil additives? There not something to be scared of, in fact they make the oil perform at its peak potential, find out more below.
The Oil Additive Package
Much of the talk about oil revolves around the basestock (which does represent around 80%), but modern oils contain so much more. Here are some of the additives that can be present in a simple can of oil. Don't get these confused with the aftermarket additves available from many retailers.
Anti-Ageing Additives (oxidation inhibitors)
At higher temperatures, oil molecules react with the oxygen in the air. In addition, metal surfaces act as catalysts to such reactions. The results of oil ageing are:
- Increase in viscosity (oil thickening)
- Formation of residues (coke, sludge, etc.)
- Corrosion resulting from the acids formed
The inclusion of antioxidants in lubricant formulations can either avoid or slow these effects. Proven oxidation inhibitors are nitrogen, phosphorous and sulphur compounds (amines, phenols together with zinc, calcium, etc.).
Detergent and Dispersant Additives (dirt carriers)
The task of these additives is to hinder the coagulation of oil-insoluble residues such as resins and asphalt-based oxidation products and thus combat sludge deposits and oil thickening.
Moreover, these additives dissolve residues (cleaning effect) and neutralise acids. These additives can sometimes include succinimides, neutral metal sulpho-nates, phenolates, phosphates, thiophosphates, polymer detergents, amine compounds, sulphonates, highly molecular organic lime, lead and zinc salts, etc.
EP Additives (Extreme Pressure additives)
EP or anti-wear additives are used to increase load carrying capacity and reduce wear in boundary friction conditions (e.g. on cams, gear teeth, tappets, etc.). They work by forming metallic surface layers which prevent roughness peaks from welding together in boundary friction conditions and enabling metal surfaces to slide without wear by reducing friction.
The following agents are sometimes used:
Zinc dialkyl dithiophosphate, tricresylphosphate,organic phosphates as well as sulphur and nitrogen compounds.
Viscosity Index Improvers (VI improvers)
These are substances (oil-soluble polymers) which improve the viscosity-temperature behaviour of mineral oils, i.e. They reduce the influence of temperature on viscosity. At low temperatures, they improve flowing characteristics and at high temperatures, they increase viscosity.
Products used include polymethacrylates (PMA), olefincopolymers (OCP), polyisobuthylenes (PIB) and styrol-butadien-copolymers (SBC).
As VI improvers are very shear-sensitive, multigrade oils with wide viscosity ranges (i.e. 5W-40, 10W-40 etc.) should be formulated with unconventional base oils (e.g.hydrocracked oils, polyalphaolefins) which have much better natural VI characteristics.
Pour Point Depressants
Oils get increasingly viscous as their temperature falls until they cease to flow and start to solidify. This is caused by the crystallisation of paraffin molecules. The inclusion of additives such as polymethacrylate, alkyl-phenols, naphthaline with chlorinated paraffins, propylenecopolymers, etc. lowers the temperature at which solidification occurs.
Polysilicones (silicone polymerisates), polyethyleneglycol esters, etc. reduce foaming caused by churning. Excess foaming (air-oil mixtures) can result in inadequate lubrication. Seizures to bearings can occur if the oil pump draws oil-air foam instead of oil
These are surface-active substances which reduce frictional losses in boundary friction conditions and create defined frictional behaviour. This improves the efficiency of machinery. The substances used include fatty acids, fatty acid derivates, organic amines, aminephosphates, etc
As you can see, these additives are extremely important components of the oil, yet in budget oils, the quality of the additive package is one of the first things to be reduced to save money. Reducing the quality of the additives is a less obvious way of reducing the quality of the oil than using a cheaper basestock oil, but as you can see from the information above, the additive package is just as important as