In today’s tighter clearance situations, oil with a viscosity that is too high can clog at or near the clearance and provide almost no protection for affected components. Oil that’s too thin, however, can lead to insufficient oil pressure, an inconsistent lubricating film, metal-to-metal contact and wear.Ĭircumstances where a higher viscosity oil makes sense are just the opposite: high load, low speed and a higher operating/ambient temperature. A lower viscosity oil makes sense in circumstances where there is low load, high speed and a lower operating/ambient temperature. As long as they provide adequate surface coverage and separation, these oils reduce internal friction better than higher-viscosity oils. Today’s advanced machinery is trending toward much tighter clearances between components, enabling the use of lower viscosity oils. The concept can be confusing, but you can think of viscosity this way: water has a kinematic viscosity of close to zero centistokes (cSt) while something like molasses is well over 1000 cSt.” TestOil Field/Data Analyst Dwon Ruffin explains, “ Viscosity is the single most important physical property of a lubricant. The tables below show examples for different crude oils and their typical values for kinematic viscosity and ☊PI.CLEVELAND Ma- TestOil, the industry leader in lubricant analysis, explains viscosity, viscosity index, the considerations for selecting industrial oil with the correct viscosity and oil analysis testing that pinpoints issues resulting from viscosity. *Different sources state a different maximum percentage of sulfur content for sweet crudes (between 0.42 % up to 1 %). Sour crude: sulfur content higher than 1 %.Sweet crude: sulfur content up to 1 % *.Intermediate oils are between these extremes.Īccording to the sulfur content, it can be distinguished between:

Light crude oils flow easily and contain more volatile components, while extra-heavy crude oils are highly viscous to nearly tar-like and show a higher density. The API degrees indicate whether a crude oil floats on water or sinks. Extra-heavy crude oil: API gravity below 10 ☊PI (higher than 1000 kg/m³).Heavy crude oil: API gravity from 22.3 ☊PI to 10 ☊PI (920 to 1000 kg/m³).Medium crude oil: API gravity from 31.1 ☊PI to 22.3 ☊PI (870 to 920 kg/m³).Light crude oil: API gravity higher than 31.1 ☊PI (less than 870 kg/m³).Crude oil's viscosity can vary from a low-viscosity liquid to up to tar-like, nearly solid form.Ĭlassification according to the API degree: Both a crude oil's viscosity and its API (American Petroleum Institute) degree are important parameters for classification. The different types of crude oil need to be classified for further treatment. Depending on its geographic origin, its chemical composition and consistency vary. Crude oil is a complex mixture of various components.

Oil and gas viscosity test