Engine Oil Additives & Formulations
Use of additives, or better yet, choosing an oil that already contains these formulations is another approach to improving and maintaining oil performance.
High engine temperatures combine with moisture, combustion byproducts (including unburned gasoline), rust, corrosion, engine-wear particles, and oxygen to produce sludge and varnish. The additives not only assist oil in maintaining good lubrication, they also help minimize sludge and varnish and the damaging effects from their formation. Listed below are some of the key additives:
Viscosity-index improvers:
This reduces the oil's tendency to change viscosity as temperature changes.
Detergents:
They remove some deposits, primarily solids, however; their main purpose is to keep high temperature surfaces clean by inhibiting the formation of high-temperature deposits, rust, and corrosion. These detergents are consumed and diminished throughout the oil change interval. Another reason to be diligent with proper oil maintenance.
Pour-point depressants:
These are used to provide good oil flow at low temperatures. Even though the oils viscosity rating is low, that doesn't mean the oil will readily flow at low temperatures. This is crucial in cold weather starting and the oils ability to protect the engine.
Dispersants:
This additive helps disperse solid particles into solution and keeping them suspended in the oil. They also prevent the suspended contaminants from forming together to form sludge, varnish, and acids.
Antioxidants:
Engine temperatures are increasing as the result of improved design for better emissions control. The antioxidants are necessary to prevent oxidation (the exposure of oil to oxygen at high temperatures), and as a result a thickening of oil, sludge and deposits.
Anti-wear agents:
As lubricating film breaks down due to high temperature and friction, the anti-wear agents must protect the metal surfaces especially on piston rings and cylinder walls. Anti-wear agents coat these surfaces and are consumed throughout the life of the oil change interval.
Friction Modifiers:
These are not the same as anti-wear agents. They reduce engine friction under high loads and temperatures, thus maintaining efficiency and fuel economy. This additive also diminishes throughout the life of the oil change interval.
Foam Inhibitors:
Foam / air bubbles are created as the crankshaft splashes through the oil in the oil pan. Foam generation makes it difficult for the oil to pump to essential engine parts and therefore, reduces lubricating and cooling properties of the oil. Foam inhibitors are used to cause the foam bubbles to collapse.
Rust/Corrosion Inhibitors:
The natural fuel combustion process creates rust and corrosion bi products. These inhibitors coat and protect the metal surfaces and pars from acids and moisture.