Oil Viscosity Explained

What It Means For You and Your Car

Perhaps you’ve stood in front of the shelves of motor oil in the parts store and wondered why there were so many choices. Aren’t all oils the same? No, they’re not. In addition to various types of oil (conventional, full synthetic, synthetic blend, and high mileage), there are different viscosities of oil. When you bring your car to AutoStream Car Care in Ellicott City, Maryland, our ASE certified technicians will help you choose the best oil for your vehicle based on the manufacturer’s recommendations, your car’s age, and your driving habits and climate conditions.

Buying By the Numbers

Motor oil’s behavior when poured varies, especially when the outside temperature changes. Viscosity describes how well oil pours at a particular temperature. Lower viscosity oil, which is thin, pours easier when it’s cold than does thicker, higher viscosity oil. Why does that matter? It’s important because lower viscosity oil is great for reducing friction between engine parts and getting moving quickly when starting your car in cold temperatures, but higher-viscosity oil is better at creating and maintaining a thick protective film over those parts. The thicker oil is also good for sustaining sufficient oil pressure when hauling heavy loads.

When purchasing oil, look for the Society of Automotive Engineers (SAE) scale. The first number before the “W” tells you how well the oil flows at 0 degrees. That’s the viscosity. The lower the number, the less the oil thickens in cold weather. The second two numbers after the “W” tell you the viscosity at 100 degrees. This is a statement of how well the oil resists thinning at high temperatures. Lower numbers thin out at a faster pace than do oils with higher numbers.

Just Let Our Experts Handle It

When choosing the viscosity of motor oil to purchase, first consult your owner’s manual to get the manufacturer’s recommendation. Beyond that, think about where you live and drive. If you do most of your driving in cold temperatures, you may want to use a lower winter viscosity oil. In hot conditions, however, you may want the higher viscosity represented by digits following the “W.” Or your only decision could be which day you’re going to bring your vehicle to AutoStream in Ellicott City, Maryland, to take care of all your oil selection and auto service needs!

Written by Doug Grills

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