Source(s): 10 years of being a mechanic, with a college degree. The scale rates oil from a low of 5 to a high of 50. The second number, 40, means that the viscosity of this multi-grade oil at 100°C (212°F) operating temperature corresponds to the viscosity of a single-grade 40 oil at same temperature.

News Sources: Rymax Lubricants, Valvoline. The News Wheel is a digital auto magazine providing readers with a fresh perspective on the latest car news. The “W” in the middle of each number set refers to “Winter.” On the left side of the “W,” that number references the viscosity of oil under colder temperatures.

Viscosity of these oils is measured at 212 degrees Fahrenheit; higher numbers indicate more viscous oil. aus oder wählen Sie 'Einstellungen verwalten', um weitere Informationen zu erhalten und eine Auswahl zu treffen.

What do all those number and letters mean? The thing to keep in mind about motor oil is that its main job is to protect your engine from wear caused by the friction created when moving parts rub against each other at high speeds and high temperatures. -- Q U E S T I O N: Motor oil: SAE 30, 10W-40, 20W-50. Of course, you can save a lot of money by doing your own oil changes.

For example, a 5W-30 oil will have the viscosity of a 5-weight oil when temperatures are cold but work as well as a 30-weight oil when the engine heats up. Generally speaking, oil with sequentially higher designation codes supersede previous codes and are compatible with engines built to run with oil from earlier designations. So, those numbers on a quart of oil? However, if you live in an extremely cold climate or just want better fuel economy, you can use a “0W” viscosity grade while keeping the recommended operating temperature viscosity grade (the second number) the same (e.g. As a result, there can be more space between the parts of a 100,000-mile engine than in the engine of a brand new car. My suggestion: Refer to the owner’s manual that came with your car.

On that happens, the oil circulation in the engine will be very poor. In such liquids, for example, viscosity may decrease as temperature rises until a critical point is reached and then the liquid may suddenly become more viscous. The standard unit of measure for viscosity is either the centistoke or the centipoise. It takes fuel to make an engine run, but it also takes oil to keep it alive. But not all liquids behave in accordance with the dictates of Newtonian Viscosity. The first number describes viscosity at low temperatures. The letters Whatever the engine oil’s viscosity, the numbers are usually preceded by “SAE,” which stands for the Society of Automotive Engineers, the organization whose viscosity standards determine the numbers.

One is for lower temperature, and other is for higher. The local auto parts store typically carried a few varieties of a few major brands, and that was about it. There is a class of fluids for which viscosity does not change in a linear fashion in reaction to pressure or heat. That is, if I don’t get nervous and forget.