When it comes to the oil that you put into the engine of your classic or late-model vehicle, do you really understand what oil it actually needs? Why do some guys feel that a 10-40 weight oil is best for their application while other feel that a 20-50 oil is a must have? Long ago, the Society of Automotive Engineers (SAE) developed a rating system for oil viscosity, which is oil’s the most basic characteristic. Often referred to as the oil’s weight, it’s expressed by four or five characters, such as 10W-30, 10W-40, etc.
When deciphering the numbers on a container of oil, the lower the first number, the better it flows in colder temperatures. The number after the dash indicates how well the oil flows when it’s warm. And contrary to popular belief, the “W” does not stand for weight, but rather, winter. The higher the numbers, the “heavier”, or more viscous the oil. Multi-viscosity oils were developed several decades ago, so typically, you don’t have to worry about using different oils for winter and summer.
For years, many enthusiasts have felt that in order to really protect the moving parts of their engine, they needed to use heavier oils like 20-50 weight. But recently, improvements in oil technology and engine building, have allowed manufacturers to specify using a lighter oil, such as 5-20. One reason is that modern engines are designed and built with tighter tolerances between crucial parts like bearings and the crankshaft than previously utilized. When the engine is cold, a heavier oil might not be able to properly flow into these tight areas, and as soon as you start the engine, damage can occur. The lighter oil will flow more easily into tighter clearances, providing much needed protection, much sooner. What many people also don’t understand, is that as an upside, a lighter oil can also help provide better fuel economy, and free some needed horsepower.
We found this video from Driven Racing Oil that will help you understand oil viscosity, and its relationship to your engine. Knowing what your engine needs can unlock improved fuel economy, reduce wear, and increase horsepower.
Resistance to thinning with increasing temperature is called an oil’s viscosity index. And although a higher second number is good, the oil also has to be robust. That is, it must be able to last for thousands of miles until the next oil change. For example, oil tends to lose viscosity from shear (the sliding motion between close-fitting metal surfaces of moving parts such as bearings). So resistance to viscosity loss (shear stability) is necessary to enable the oil to maintain the lubricating film between those parts.
Walk into any auto parts store, and you’ll see a lot of different oils on display. There are specific oils for high-tech engines, new cars, high-mileage vehicles, heavy-duty/off-road vehicles, etc. In addition, you’ll also see a wide selection of different oil viscosities. In this video, Lake Speed Jr., Certified Lubrication Specialist at Driven Racing Oil, takes the time to go into detail about just what all those various viscosity numbers and letters actually mean. Speed also makes it simple to understand by using a real world example–Maple syrup and pancakes–to demonstrate oil thickness, and clarify the difference between viscosity grade and viscosity index.
So if you’re not sure what oil your engine actually needs, check out Driven Racing Oil, and you can find any oil related information that you are looking for.