In 5w30 what does the 5 stand for and what is the 30?

Question

Is it half 5 weight oil and half 30 weight?

Answer 1

If you use 5W30 oil as an example

5 is the viscosity of the oil when cold.

W stands for "cold weather approved" or "winter"

and 30 Stands for the viscosity of the oil at engine operating temperature.

Answer 2

The easiest way to answer that, your oil is thick when it cold, like pancake syrup, then when the engine warms up, it thins out, like water.  

Answer 3

The 5 means the oil has the same consistency, when cold, as cold 5 weight motor oil. The 30 means that the oil, when hot, has the same consistency as hot 30 weight oil.

Answer 4

The numbers indicate the viscosity or "thickness" of the oil.  Since modern oils have viscosity extenders added to them, they are multi-viscosity oils.  That is; they behave like one viscosity when they are cold, and another when they are warm.

So 5w30 is a 5 when cold and a 30 when warm.

Answer 5

The numbers stand for the viscosity rating of the oil. A 5w-30w is a blend which is equivelant to a 5 weight and a 30 weight. Lighter oils are thinner and usually used in colder climates. A 30 weight is for normal use. Hope this answers your question.