Dynamic vs kinematic viscosity
Synthetic lubricants, such as AMSOIL synthetic lubricants offer better cold-flow when the temperature drops and improved protection once your engine has reached operating temperature. Not only that, but you want to use a lubricant that resists thickening when cold, yet maintains its ability to protect against wear when hot.
The key is to use a lubricant with the correct viscosity for the application. Different vehicles require different viscosities If the viscosity is too high, fluid friction generates excessive heat that shortens the lubricant’s life. Furthermore, high viscosity or speed may also increase the lubricant’s film thickness, which increases fluid friction. As speed increases, components may require a lower-viscosity oil to operate efficiently. Whether the application is a grease-filled bearing or oil-filled gearbox, one must consider the lubricant’s optimal viscosity based on the application’s running speeds. What effect does speed have on lubrication? Optimizing viscosity ensures oil can circulate properly and provide adequate film strength on components. However, viscosity that is too high can cause oil starvation by not flowing through small oil passages. Applying extreme pressure to oil can lead to mechanical shear, which lowers the film strength and leads to metal-to-metal contact and wear. Proper viscosity for the intended application is critical to ensure that forces applied to the oil do not result in increased component wear. If the viscosity is too high, it won’t flow as readily and your engine will work harder and burn more fuel. But there are limits to this relationship. The greater a lubricant’s viscosity, the greater pressure or load it can withstand, allowing separation between moving parts to be maintained. If it becomes too thin, it can fail to adequately separate metal components during operation, inviting wear. The intense heat your engine generates causes the oil to become thinner. Say you’re towing a camper down the interstate at the height of summer. The opposite happens when the temperature soars. Since the oil flows more slowly, engine components may be vulnerable to wear until the oil warms enough to flow throughout the engine. That’s why it may be tougher to start your car on a frigid winter morning – the crankshaft has to churn through cold, thick oil before it spins fast enough for the engine to start. When cold, lubricants thicken and flow more slowly and require more energy to circulate.
Using lubricants with too high of a viscosity for the application may lead to the following issues: Using lubricants with inadequate viscosity for the application may lead to these issues: How lubricant viscosity reacts to changes in temperature, pressure or speed determines how well the oil protects your vehicle.
So what does this all mean to protecting your engine? Put simply, viscosity is the most important property of a lubricant. How does viscosity affect engine protection? The tighter the molecular bonds, the stronger the inter-molecular forces. The looser the molecular bonds, the weaker the inter-molecular forces. This is essentially how molecules are bonded in liquids. If you weave through both groups and break through the chains of people, you have an easier time weaving through the first group than the second. On the other side of the room, everyone is holding hands fairly tightly. It’s flu season and they don’t want to get sick. In one group everyone is holding hands very lightly. Let’s think of molecules as a group of people in a room. Dynamic viscosity determines an oil’s low-temperature grade (the “5W” in 5W-30). It takes less energy to stir water compared to honey because the Dynamic viscosity of water is lower.
DYNAMIC VS KINEMATIC VISCOSITY SIMULATOR
Measured by the Cold Crank Simulator (CCS) test (ASTM D5293), is defined as the lubricant’s resistance to flow as indicated by its measured resistance, best thought of as the amount of energy required to move an object, such as a metal rod, through the fluid.