These lower viscosity motor oils are needed to move through the thin engine pathways to protect and clean metal surfaces. This has led over time to motor oil viscosity decreasing – currently 5W-30 and 5W-20 are the most popular grade and 0W-20 is the fastest growing grade. But as engine technology has advanced over the years, the size of engines and pathways in engine that oil flows through have gotten smaller and thinner. In the past, it was common for vehicles to require higher viscosity oils such as 20W-50’s, 10W-40’s and 10W-30’s. The 5W-20 will have a lower viscosity and provide less resistance than the 10W-30 at both start-up and normal engine operating temperatures. If we compare a 5W-30 and a 10W-30, they will behave very similarly as the engine heats up, but at start-up, the 5W-30 will provide less resistance and start easier than the 10W-30. Less resistance results in improved fuel economy but the oil is not as thick and forms a smaller layer of protection between metal surfaces. But as the engine heats up, the 5W-20 will move with less resistance than an 5W-30. Again, the lower the number, the lower the viscosity of the oil and the faster the oil will move around the engine.Īs an example, let’s compare 5W-20, 5W-30 and 10W-30 motor oils. A 5W-20 and 5W-30 will have very similar if not equal viscosity at lower start-up temperatures. In the 5W-30 example, the 30 defines the viscosity of the oil at normal engine temperatures. The high temperature viscosity is the number after the dash and is related to the viscosity of the oil as it is moving around your engine after the car has warmed up and is at normal engine temperature. The lower the number, the faster the oil will flow at vehicle start up. For example, if the oil is a 5W-30, the 5W part describes the viscosity of the oil at low temperatures. That value has the letter “W” after the number and has a dash after the W. The low temperature viscosity of the oil is a measurement that simulates starting a car on a cold winter day. But as motor oil technology advanced, additives such as viscosity index improvers allowed for the use of the same grade of oil year-round. Years ago, most vehicles used one viscosity grade oil in the summer and a different viscosity grade oil in the winter. The measurement of viscosity at high and low temperatures are properties of multi-grade oils. Motor oil viscosity grades are based on a scale developed by the API (American Petroleum Institute) lubricant organization. The values are defined in a specification known as API 1509 and are based on the resistance the oil gives to flowing at two different temperatures – cold and high temperature. Use of the wrong oil (e.g.Viscosity is the resistance to flow of a fluid.Degradation of VI improvers (additives).Contamination by foreign substances (combustion residues, water).Varnish formation (varnish and sludge formation).Oxidation (oxygen input into the oil), degradation of oxidation inhibitors (additives).Both cases are not desired because the oil no longer optimally fulfils the required lubricating properties for the application.Ĭauses for the increase in viscosity are: The viscosity of the oil can either increase or decrease. If this happens the oil should be changed. ![]() If the viscosity of the oil deviates greatly from the initial values of the fresh oil, this is an indication that accelerated oil aging has occurred. Not only does oil change its viscosity due to temperature influences and pressure, but the environmental influences during operation can also have a lasting effect on the flow properties. In addition, the viscosity index of oils can be artificially increased by adding high-performance additives (VI improvers). In the meantime, the scale has reached values of up to 400, due in part to modern production processes for temperature-stable synthetic oils. The viscosity index started at 0 (very temperature-dependent oils) and went up to 100 (oils with low temperature dependence). ![]() When the viscosity index was developed in 1928, the scale was based on the mineral oil types known at the time. Their lubricating properties become unstable at high or low temperatures. The oils with a low viscosity index can be influenced more strongly by the temperature. The oil retains its lubricating properties in a wider temperature range. Oil with a high viscosity index is less temperature dependent. To a certain extent, the viscosity index is also an indication of the quality of an oil and serves the comparability of different oil types. The viscosity behaviour at 40 ☌ and 100 ☌ is measured. It refers to the kinematic viscosity of an oil. The viscosity index (VI) is the behaviour of the lubricant as a function of temperature.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |