Understanding the difference between an oil’s viscosity grade and its viscosity index will go a long way in selecting the right lubricant for any engine. That’s according to Lake Speed, Jr., a certified lubrication specialist for Driven Racing Oil. He’s just released a quick but highly informing video titled “Viscosity 101.”

“Viscosity is the single most important property of a lubricant,” says Speed to open the conversation.

In simple terms, viscosity is the measurement of a fluid’s resistance to flow. Since temperature affects viscosity, engines need a thicker oil when run hot and a thinner oil for easy startup under cold conditions. During the Golden Age of the automobile, owners had to switch between summer and winter oils. Then the oil companies developed multi-grade oils that serve both hot and cold seasons.

Basically, the viscosity grade represents the thickness of the oil and the viscosity index represents how it reacts to temperature change. Speed then differentiates between early mineral oils, synthetics and the new synthetics developed with mPAO base stocks.

The video features plenty of easy-to-understand analogies and references to specific racing applications. So, if you’re still in dark about today oils, check out this video from Driven. And for a deeper dive into race oils and how they compare to street oils, follow this link.