Understanding engine oil terminology
By Bardahl • The 1/12/2021 • 5 min reading
The strange codes you see above are the viscosity ratings of multi-grade oils. Don't worry, we'll explain. There are several types of oils: single-grade and multi-grade. Multi-grade oil has the advantage of adjusting its viscosity with heat, meaning its viscosity increases as the engine temperature rises. Thus, it has two viscosity grades (hot and cold).
Viscosity: definition
And what is viscosity? It refers to the thickness, which represents the resistance of the fluid as it flows. The higher the viscosity of an oil, the thicker it is. It will therefore take longer to flow, but its protective film for mechanical parts will be of high quality.
Hot, cold
For an oil, you understand, temperature is crucial! And it’s this degree of hot or cold that you find in a multigrade oil index. Take "5W30" for example. This means that the viscosity at cold (the "W" stands for "Winter") is 5 and 30 when the engine is hot.
It is preferable to use multigrade oils because they have a low viscosity at low temperatures. They are "light." This means that the lubricant flows quickly and reaches the moving parts sooner when the engine starts, cold. But their composition also allows for an increase in viscosity, hot, when the engine also needs optimal lubrication. And for your two or four-wheeled companion, it's essential!
SAE, ACEA, API, S, C, etc.
Oils each have their chemical characteristics that depend, among other things, on the regions where they will be used (the outside temperature is not the same in Paris as in Dubai!). They meet the needs of different manufacturers. These characteristics vary, for example, for a car equipped with or without a particulate filter (DPF).
On oil can labels, you might see SAE, which stands for Society of Automotive Engineers. This organization introduced a coding system for motor oils based on their viscosity. However, each region of the world has its own standards for its manufacturers: SAE (Society of Automotive Engineers) for the US, ACEA (Association des Constructeurs Européens d’Automobiles) for Europe, and API (American Petroleum Institute) for American vehicles, or JASO (Japanese Automotive Standard Organization) for the Japanese automotive industry.
You might also encounter the letters S and C: S indicates that the oil is used for gasoline engines, and C for diesel engines.