What does the “w” stand for in multigrade oils?
The “w” stands for winter.
Let’s go back a bit. We weren’t always as advanced in lubricant technology as we are today. For instance, if we left an ice tray filled with water on the table, what would happen? It would remain in that state of water. Now, if we placed that in the freezer, the water would turn into ice.
Similarly, before we advanced lubrication technology, there was one oil to be used for the Summer and one for the Winter. During the summer, the temperatures were higher and during the winter the temperatures were lower.
The “w” helps us to understand that this is the measurement related to how an oil flows at a cold temperature (or on start-up). It does not mean that you can only use an oil with a “w” in countries that experience winter!
The lower the number is in front of the “w”, the faster the oil flows on start-up. When we start our cars on a morning, all of the oil is at the bottom of the sump. It will take some time before the oil gets from the bottom to the top of the engine.
However, all of the parts in the engine are moving before they get the oil. Thus, it is critical to get the oil to them in the shortest time possible. The lower the number in front of the “w”, the faster the oil takes to get to the top of the engine (this will reduce the amount of wear that occurs).
Quick Tip: Zero (0) does not mean that there is no protection on start up, it means that it will get to the components faster than all the other grades (like a 0w20).
What about the number after the “w”?
This is the number that represents the viscosity of the oil at operating temperature. When the engine begins operating this is the viscosity that flows through all of the lines and components continuously. As we mentioned in an earlier post, the value has decreased in recent times (some going as low as 0w16!) due to the lines being thinner, which is ideal for lower viscosities.