Quick Links
Get in touch with us today to learn more about our products
What You Need to Know Part 2
In part 1 we talked about what motor oil is made of, base stock and additives. Today we will talk about 7 functions or โjobsโ a motor oil has inside your engine.
What must a motor oil do?
Modern motor oils are highly specialized products carefully developed by engineers and chemists to perform many essential functions. The additives in a motor oil are what give it its qualities to help with its performance. The jobs a motor oil must do are: friction reducer, cleaning, cooling, lessen shock on parts, prevent rust, and seal the combustion chamber
Minimize Friction
Lubricants reduce contact between components, minimizing friction and wear. They accomplish this by leaving a thin film on the surfaces of parts.ย The ability of an oil to remain โstuckโ to a part and coating it after long periods of โsitting stillโ is a major preventer of wear during a โcold startโ.ย A โcold startโ refers not just to cold temps, but also refers to engines that havenโt been started in a while, like overnight.ย Studies have shown that cold starts are where most engine damage occurs.
Cleaning powerย
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.
The place where oil works hard.
While the solvency of the oil is important, detergents and dispersants play a key role. Detergents are additives that prevent contaminants from adhering to components, especially hot components such as pistons or piston rings. Dispersants are additives that keep contaminants suspended in the fluid. Dispersants act as a solvent, helping the oil maintain cleanliness and prevent sludge formation.
Cooling
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.
Fun Fact: Lubricating an engine requires a very small amount of motor oil compared to the amount needed to ensure proper cooling of all these internal parts.
Seal
Motor 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 motor 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 componentโs 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.
Fun Fact: Motor oil has no natural ability to resist rust and corrosion; those properties must be added through use of motor oil additives.
Transfer Energy
Because motor 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.
As you can see, modern motor oils have many functions or โjobsโ they must complete, especially as todays engines become smaller, produce more horsepower, increase fuel mileage and help reduce emissions.ย These goals all increase the workload of motor oils and producing an oil that accomplishes all these tasks takes time and testing to get the right balance. However, the correct balance of additives will help your motor oil protect your engine and make it last longer.
ย
What is viscosity?
Viscosity refers to the oilโs resistance to flow and is the most important property of an oil. The viscosity of oil varies with changes in temperature โ thinner when hot, thicker when cold. Although 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.
Wouldnโt it be handy to have a number that indicated the oilโs viscosity change? We do, and itโs called the Viscosity Index (VI). It is measured by comparing the viscosity of the oil at 40ยฐC (104ยฐF) with its viscosity at 100ยฐC (212ยฐF). The higher the VI, the less viscosity changes with temperature changes, and the better the oil protects the engine. Synthetics typically have a higher VI than conventional oils.
SAE viscosity grades
For engine and gear oilsย accordingย to the SAE standards J 300 and J 306
SAE stands for Society of Automotive Engineers. The SAE developed a classification system to define the viscosity or thickness of oil. This system has been progressively modified over the years. It defines โoperating temperatureโ engine oil viscosities for different grades and contains specifications for โcrankingโ viscosity andย pumpabilityย at start up, the โWโ grades or winter. A multigrade oil is one that meets both a โWโ low temperature viscosity requirement and a 100ยฐC โoperating temperatureโ requirement.ย 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
For engine oils there is a specification that must be met at 150ยฐC, known as a High Temperature/High Shear (HT/HS) viscosity. HT/HS simulates what happens in high stress areas of the engine e.g. bearings, cams, etc. It measures the viscosity and indicates the oil film thickness under severe high-speed conditions. An oil that is too thin under these conditions may not provide the required protection to prevent significant wear in these critical engine parts.
Centipoise (cP) and Centistokes (cSt) are the units viscosity is measured in. The following chart shows a comparison of different viscosity grades versus temperature rang.
ย