Car engine oil is one of the most important factors in your engine’s performance and longevity. Put simply, it’s the lubricant that prevents all those metal parts from tearing each other apart or welding themselves together. Without car engine oil, your engine would destroy itself in a matter of seconds.
Car engine oil contains two fundamental components: base oils and additives. The two work in tandem to produce the final product you put in your engine.
- What is the function of engine oils?
- Types of Engine Oils
- Viscosity Grades
- Advantages and Disadvantages
- Recommended Engine Oils
What is the function of engine oils?
Minimize Friction
Lubricants reduce contact between components, minimizing friction and wear.
Clean
Lubricants maintain internal cleanliness by suspending contaminants within the fluid or by preventing the contaminants from adhering to components. Base oils possess a varying degree of solvency that assists in maintaining internal cleanliness. Solvency is the ability of a fluid to dissolve a solid, liquid or gas.
Detergents help keep critical components, like the pistons, clean and functioning properly.
While the solvency of the oil is important, detergents and dispersants play a key role. Detergents are engine additives that prevent contaminants from adhering to components, especially hot components such as pistons or piston rings. Dispersants are engine additives that keep contaminants suspended in the fluid. Dispersants act as a solvent, helping the car engine oil maintain cleanliness and prevent sludge formation.
Cool
Reducing friction minimizes heat in moving parts, which lowers the overall operating temperature of the equipment. Lubricants also absorb heat from contact surface areas and transport it to a location to be safely dispersed, such as the oil sump.
Seal
Car engine oil acts as a dynamic seal in locations like the piston ring/cylinder interface. A dynamic seal helps keep combustion gases in the combustion chamber, which maximizes horsepower and helps prevent hot gases from contaminating the car engine oil in the sump.
Dampen Shock
A lubricant can cushion the blow of mechanical shock. A highly functional lubricant film can resist rupture and absorb and disperse these energy spikes over a broad contact area. As the mechanical shock to components is dampened, wear and damaging forces are minimized, extending the component’s overall operating life.
Protect Against Corrosion
A lubricant must have the ability to prevent or minimize internal component corrosion. Lubricants accomplish this either by chemically neutralizing corrosive products or by forming a barrier between the components and the corrosive material.
Transfer Energy
Because car engine oil is incompressible, it makes an excellent energy-transfer medium, such as when used with hydraulic valve lifters or to actualize components in an engine with variable valve timing.
Types of Engine Oils
- Mineral Oil
- Semi Synthetic Oil
- Synthetic Oil
- High Mileage Oil
Mineral oils are formulated in a variety of viscosity grades and quality levels. They are recommended for drivers with simple engine designs and regular driving styles. Drivers with a heavy foot or varied driving styles are highly recommended to go for synthetic oils, they have a longer service life and oil drain interval too! Mineral oils are refined from crude oil. Contaminating elements such as sulphur, nitrogen, oxygen and metal components such as nickel or vanadium are inherent to crude oil and cannot be completely removed through the refining process. The oil refining process separates the various types of molecules in the oil by weight, leaving molecules similar in weight but dissimilar in structure, reducing performance.
Semi-synthetic oils use a mixture of synthetic and mineral oils for added resistance to oxidation in comparison to mineral oil and at the same time provide excellent low-temperature properties for your beloved engine.
Synthetic oils are chemically engineered, the oil molecules are therefore more uniform in shape with fewer impurities and better properties than mineral oils. As synthetic oils are formulated with higher performing additives, they tend to perform better at extreme ends of the temperature spectrum, be it high or low. Synthetic base oils are highly engineered to include only beneficial molecules. As such, synthetic base oils contain no contaminants or molecules that don’t serve a designed purpose. Their versatility and pure, uniform molecular structures impart properties that provide better friction-reduction, optimum fuel efficiency, maximum film strength and extreme-temperature performance conventional lubricants just can’t touch.
High-mileage oils are specially formulated for older vehicles or newer vehicles with over 100,000 kilometres on the odometer. High mileage oils, with a special blend of additives and formulation, helps to reduce burn-off of engine oil and concurrently helps to prevent oil leaks that may occur in older or high-mileage engines.
Additives
The various chemicals that comprise a car engine oil’s additive system provide anti-wear, anti-foam, corrosion protection, acid neutralization, viscosity maintenance, detergency and dispersancy properties. A few examples of chemical additives include zinc, phosphorus and boron. Striking the perfect balance of the proper engine additives in relation to the base oil is a tough balancing act for oil formulators, especially as vehicles grow more demanding and sophisticated.
Viscosity Grades
Viscosity is a car engine oil’s most important property. The lower the viscosity, the faster the oil flows, like water. Thicker oils flow more slowly, like honey.
Viscosity refers to the car engine oil’s resistance to flow and is the most important property of an oil. The viscosity of oil varies with changes in temperature – thinner when hot, thicker when cold.
Although car engine oil must flow at cold temperatures to lubricate the engine at startup, it must also remain thick enough to protect the engine at high operating temperatures. When an oil is used at a variety of temperatures, as with most engines, the change in viscosity should be as minimal as possible.
Wouldn’t it be handy to have a number that indicated the oil’s viscosity change? We do, and it’s called the Viscosity Index (VI). It is measured by comparing the viscosity of the oil at 40°C (104°F) with its viscosity at 100°C (212°F). The higher the VI, the less the viscosity changes with temperatures changes and the better the oil protects the engine. Fully synthetic oils typically have a higher VI than conventional oils.
The Society of Automotive Engineers (SAE) has developed several viscosity classifications or grades, such as 5W-30, 10W-40 and 15W-50.
These SAE viscosity grades designate the specific ranges in which the particular oil falls. The “W” indicates it is suitable for use in cold temperatures. (Think of the “W” as meaning “Winter.”) The classifications increase numerically; the lower the number, the lower the temperature at which the oil can be used for safe and effective engine protection. Higher numbers reflect better protection for high-heat and high-load situations.
The overwhelming majority of oils today are multi-viscosity, meaning they behave differently at different operating temperatures to provide the best of both worlds – good cold-flow when the temperature drops and reliable protection once the engine reaches operating temperature. For example, a 5W-30 car oil performs like an SAE 5W at 40ºC and an SAE 30 car oil at 100ºC.
