Choosing the right motor oil can be confusing for the average car owner. Not only must you consider different brands and whether to go conventional or synthetic, but you must also pick the correct SAE viscosity grade.
What does SAE stand for in oil?
SAE is short for Society of Automotive Engineers (now SAE International). The group is responsible for establishing the code system used for grading motor oil viscosity. With a universal rating system in place, 5W-30 oil means the same thing with one oil brand as it does with another.
In this guide, I’ll provide more information about oil viscosity and SAE grades, like what happens if you choose the wrong grade, how to pick the correct grade, and more.
Let’s get started.
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Why Is Viscosity Important In Motor Oil?
Motor oil lubricates your car’s engine, keeping friction at bay and reducing wear. Viscosity refers to how fluid something is, how thick its consistency is, and for oil, how much resistance there is as it flows within specific temperature ranges.
Viscosity matters with oil because your engine’s moving parts may fail to remain lubricated if it’s too thin. Whereas your motor will work harder and may have trouble starting if it’s too thick. None of these cases are ideal.
The goal is to use a viscosity that’s just thick enough to create a strong film of protection between moving parts, but not so much that it stresses the engine.
You must also account for different climate conditions since viscosity changes with temperature.
Thankfully, once you understand the SAE grading system, you’ll easily be able to choose the right oil for your car.
SAE Viscosity Grades Explained
The SAE designed a test that measures how fast oil flows through an opening. The longer it takes, the higher its viscosity grade (also known as oil’s “weight”).
When shopping for motor oil, you’ll find a product’s SAE grade right on the packaging. Look for something like 5W-30 or 10W-40.
The first character indicates the oil’s viscosity at low temperatures. The W that proceeds it stands for winter. The lower the number, the less likely it is to thicken in cold temps.
Low-temp weight is crucial when you live where it freezes overnight. Too thick, and your vehicle may not start in the morning.
The last two characters refer to the oil’s viscosity at regular operating temperatures.
Thinner oil is more common in newer cars, but if you’re using oil that’s too thin, the protective film may break down in higher temperatures, increasing friction and wear.
Learn more about motor oil viscosity differences in our detailed guide.
How To Choose The Correct Viscosity Oil For Your Car
Some of the most common grades of motor oil are 5W-40, 5W-30, and 5W-20, especially on light passenger cars. 0W-20 is also becoming more popular in newer cars with high-performance motors, like those with turbochargers.
The best SAE oil viscosity grade to use in your car is the one that’s made for it, which you’ll find printed in its owner’s manual. You should also see your car’s recommended oil weight on the inside of the oil cap.
However, in some cases, you may need to adjust the weight of the oil to compensate for outside temperatures. Your engine will perform better through a cold winter using lighter motor oil, while heavier oil will better protect the engine during a hot summer.
Just make sure to stick within the manufacturer’s recommended SAE viscosity range.
What Happens If You Use The Wrong Viscosity Oil?
You won’t cause any immediate harm to your vehicle by using motor oil that’s off by a grade or two. But doing so may shorten your engine’s lifespan.
If you put too thin of oil in your car, friction can build and cause premature wear. Add oil that’s too thick, and you unnecessarily stress the engine. Moreover, if you live somewhere where it gets cold at night, you risk not being able to start the engine in the morning.
Some signs suggesting you’re using the wrong viscosity oil include burning odors, odd engine noises, oil leaks, and a drop in fuel economy.
What Does SAE Mean To You As A Car Owner?
Seeing SAE on the front of an oil carton simply means it follows the same grading system as any other with the label. If a product’s SAE rating matches what’s required for your vehicle, then it will work with the engine.
If you’re about to add oil that’s outside the suggested range, pause and reconsider what you’re doing.