![]() ![]() In my view, this is a very poor classification scheme. Most of the time, this viscosity is reported as the oils’ “weight”. Oils are classified in families of viscosity. This consideration for VI is important and can be confusing when, for example, buying two oils of the same viscosity classification. Mineral oils have VIs below 100, PAO synthetic oils around 150, while high-oleic canola oil has a VI of 220. High performing suspension oils sometimes have Vis in the range 300-400. Most lubricants, food grade or not, are based on mineral or synthetic oils of specific viscositiesĪ viscosity index below 100 is considered low, while a VI higher than 200 is considered very high. You do not want your oil to seize at low temperatures but also not to lose all viscosity at higher temperatures. The key characteristic of a high VI oil is its ability to withstand decreases in viscosity as a function of increasing temperature. The viscosity index of an oil refers to the difference in viscosity between 40 oC and 100 oC. Polymerisation of this alpha-olefin results in the formation of synthetic oils of different viscosities and with added benefit of higher viscosity index than mineral oils. The most common monomer used in synthetic oil manufacture is alpha-olefin, a six-carbon primary alkene. Synthetic oils are usually of higher purity and offer thus a higher performance. Most lubricants, food grade or not, are based on mineral or synthetic oils of specific viscosities. This would lead to a catastrophic failure of the machine’s moving parts. If the moving metal surfaces come too close, metal-to-metal contact will lead to surface damage (scarring), and if the heat becomes high enough, surfaces can melt and fuse. The main functions of a lubricant are to decrease the friction coefficient between moving surfaces, thus improving on machine performance with smaller energy inputs, as well as to help dissipate frictional heat.
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