10W40

Global Lubricate 10W-40 is the viscosity, or weight, of the motor oil as defined by the Society of Automotive Engineers (SAE for short).

A 10W-40 oil has a viscosity grade of 10W at a low temperature and 40 at a higher temperature.

What does this mean, exactly? 
Motor oil thickens when it’s cold and becomes thinner when heated up. 10W40 engine oil doesn’t gain viscosity when it heats up. It just behaves like a 10W weight oil when cold and like a 40 weight oil at hot.

Let’s break 10W-40 down a little further.

The 10W rating: 
The 10W represents the oil’s cold viscosity.

Oils have a specified maximum viscosity at a cold temperature. The lower the W number is (“W” stands for Winter), the thinner the oil will be. In this case, a 10W rated oil will be thicker in winter than a 5W oil.

The 40 rating:
The 40 represents the oil’s viscosity at hot temperatures. It looks at how well the oil flows at an engine running temperature of 100^oC (212^oF). The hot viscosity rating focuses on seal leakage and oil’s ability to protect engine components when it’s in a thinner state.

A 40 weight oil will be thicker than a 30 weight oil at engine operating temperature.

Now that we know what 10W-40 means, let’s see where this oil is used.