Engine oil . Oil that is used to lubricate various internal combustion engines. While the primary purpose is to lubricate moving parts by reducing their friction, motor oil also cleans, inhibits corrosion, improves sealing, and reduces engine temperature by transmitting heat away from moving parts. Motor oils are derived from synthetic chemical compounds in petroleum and other products used to make synthetic oil. Motor oil consists mainly of hydrocarbons, organic compounds made entirely of carbon, and hydrogen .
The common metric measure of absolute viscosity is the Poise , which is defined as the force required to move a square centimeter of area on a parallel surface at the rate of 1 cm per second, with the surfaces separated by a 1 cm lubricating film. of thickness. Viscosity varies inversely proportional to temperature. Therefore, its value is useless if it is not related to the temperature at which the result is reported.
The Importance of Correct Viscosity Viscosity is the most important lubrication characteristic of any machine. If the oil viscosity is too low for the application, the wear is greater due to the lack of a hydrodynamic mattress. If the oil viscosity is too high for the application, the energy consumption is higher and the wear can be greater due to lack of circulation. Only the correct viscosity will maximize the life and efficiency of the engine, transmission, hydraulic system or whatever the application.
An oilthin is less resistant to flow, so its viscosity is low. A thick oil is more resistant to flow and therefore has a higher viscosity. Oil viscosities are normally measured and specified in centistoke (cSt) at 40 ° C or 100 ° C. This viscosity is often referred to as dynamic viscosity or kinematic viscosity. This is the absolute viscosity divided by the density of the oil. In practice it is determined by measuring the time it takes for a specific amount of oil to pass through a capillary tube by gravity at 40 ° C and / or 100 ° C. By this same definition we can see that the more viscous oil offers more resistance and consumes more energy to move and allow the movement of the parts of the engine, reducer, transmission, hydraulic system or any other system that we have.
The oils are labeled with the Grade. SAE 20W , SAE 30W , SAE 40W SAE 50W etc. Some are Multigrade: SAE 5W- 30 – SAE 10W- 40 SAE 20W – 50 etc. The more degrees the oil has, its viscosity is higher, that is, it is thicker, more pasty. Multigrade oil differs due to the fact that in its chemical composition it contains substances that react to heat causing the oil to increase its viscosity. In other words, for example a SAE 10-40W multigrade oilWhen it is cold, its viscosity (thick, pasty) is 10W; and when the engine heats up the oil increases its viscosity until reaching 40W, at most it is understood that when we say: “it increases its viscosity” we are not referring to the fact; that an oil when heated by logic becomes thin; but the chemical composition of the multigrade oil adjusts to this variation, compensating and maintaining the viscosity [10W], withstanding the high temperature.
Today, monograde oils have been gradually displaced by multigrades around the world, monograde oils are still used in applications such as competitive engines, industrial equipment that operates 100% in high temperature applications, and special engine design conditions that do not allow the use of a multigrade.
In the case of a 20W 50 oil , many people think that 20W is the grade of oil for low temperatures and 50 is the grade for high temperatures, although there is some logic, there are also great differences, if this were true, an oil 20W 50 would be grade 20 at low temperature and 50 at high temperature, that means that this oil would “increase its viscosity” with the change in temperature, which physically does not occur. The reality is that the 20W 50 oil has a higher viscosity at low temperatures and as it is heated it loses viscosity.
The number 20W refers to the ease with which the oil can be “pumped” in low temperatures, the lower the number “W”, the better its fluidity properties and will facilitate starting the engine at low temperatures. The “W” stands for Winter – Winter.
A 5W 50 oil is better than a 20W 50 in low temperature starting, that is the real meaning of the first number “Ease of starting in low temperatures”, the second term is the degree of viscosity of the oil in the normal operating temperatures of the motor and is determined by the kinematic viscosity of the oil at 100 ° C.
Once the engine has started and the engine reaches normal operating temperature, the oil works as a SAE 50 degree, this is the viscosity with which the engine is protected most of the time, the advantage of multi-grade oils is its flexibility to protect the engine at start-up, with a low viscosity and that allows oil to reach the high parts of the engine quickly, to protect it against wear and subsequently to maintain a correct viscosity for the time it operates in “normal” conditions “of temperature that are regulated by the engine’s cooling (cooling) system.
To achieve this effect, an additive called a viscosity index improver is added to the oil in the oil formulation. This polymer expands as the temperature increases, somewhat compensating for the thinning effect caused by the increase in oil temperature.
The oil by nature will become thinner with temperature, the important thing in multigrades is how much you lose weight. Modern engines require an oil with excellent fluidity characteristics at low temperatures and that maintain the proper viscosity at normal operating temperatures, to efficiently protect the engine by helping it extend its life