What Does 5W-30 Stand for Anyway?
By: Parts for Trucks
Have you ever been standing in the oil aisle asking yourself what the codes on the bottle really mean? Sure, I know my truck needs 5W-30, but what’s the difference between it and 5W-40 or 10W-30?
5W-30 and 10W-30 are what’s known as multigrade oils: motor oils that are formulated to maintain their viscosity, or thickness, over a wide range of temperatures. These contrast with single-grade oils, which have a fixed viscosity and may become too thick or too thin at certain temperatures.
One of the main advantages of using a multigrade oil is that it can help to improve the performance of an engine in a variety of different temperature conditions. For example, a 5W-30 multigrade oil will have a low viscosity at cold temperatures (as indicated by the “5W” part of the code), which allows it to flow easily and lubricate the engine’s moving parts when the engine is cold. At the same time, the oil will also have a higher viscosity at higher temperatures (as indicated by the “30” part of the code), which helps to protect against overheating and reduce wear and tear on engine parts.
Digging deeper, the “W” stands for “Winter” and indicates how well the oil flows at low temperatures. The number before the “W” indicates the oil’s viscosity at -17 degrees Celsius (0 degrees Fahrenheit), with lower numbers indicating a thinner or less viscous oil. The “30” refers to the oil’s viscosity at 100 degrees Celsius (212 degrees Fahrenheit), with higher numbers indicating a thicker or more viscous oil.
So, in the case of 5W-30 oil, the “5” means that the oil has a low viscosity at low temperatures, making it easier to start the engine in cold weather, while the “30” indicates that it has a medium viscosity at high temperatures, providing good lubrication and protection to the engine when it gets hot.
But what do those numbers really mean? They are representative values of viscousness on a scale. The viscosity scale is generated using standardized tests that measure the oil’s resistance to flow at different temperatures. The most commonly used scale is the Society of Automotive Engineers (SAE) viscosity scale, which assigns a number to the oil based on its kinematic viscosity.
Kinematic viscosity is the measure of a fluid’s resistance to flow due to its internal friction. It is typically measured in units of centistokes (cSt) and is determined by measuring the time it takes for a fixed amount of oil to flow through a standard-sized opening at a standardized temperature.
In addition to the SAE viscosity rating, motor oils may also have additional performance specifications, such as API (American Petroleum Institute) and ILSAC (International Lubricant Standardization and Approval Committee). These ratings indicate the oil’s performance in terms of its ability to reduce engine wear, its detergent and dispersant properties, and its resistance to thermal breakdown.
In summary, SAE viscosity multigrade oils are a type of motor oil that is formulated to maintain their viscosity over a wide range of temperatures. This can help to improve the performance of an engine in different temperature conditions and protect against overheating and wear and tear on engine parts. Always consult your vehicle owner’s manual or a mechanic to determine the appropriate viscosity oil for your specific make and model of vehicle.