Decoding the "Donuts"

The API (American Petroleum Institute) symbol on motor oil labels is also called a donut. It unlocks a lot of cool and critical information that can help you choose the ideal motor oil. Let's nibble away at the donut to understand its true meaning.

Top of the Donut – Performance Level Indicators

See the two letters at the top? The first signifies engine type. If you see an "S," that oil is designed for gasoline vehicles. A "C" means diesel. The second letter represents quality. For the most protection from power-robbing deposits watch that second letter. The higher it is, the higher the performance quality. "SM" is tops for gasoline engines.

Center of the Donut – Viscosity Grade Identifiers

Right in the middle is where you can focus on viscosity, which relates to oil flow at different temperatures. Look for the SAE (Society of Automotive Engineers) mark. The lower the number on the left, the thinner the oil at low temperature, and the happier your engine will be in cold weather when it's time to turn over. The number to the right relates to higher temperatures. Higher numbers indicate thicker oil for better performance in the heat. The "W" stands for Winter Grade.

Multi-grade oils carry a dual-viscosity grade so they perform well in high or low temperatures. Now when you see identifiers such as 10W-30, 5W-20 or 20W-50 you'll know what it means – winter on the left (go lower), summer on the right (go higher).

Bottom of the Donut – Energy Conserving Properties

Down below, oils with fuel-saving ability that pass standard industry tests are labeled as Energy Conserving. With rising gas costs, it's nice to know if your motor oil also provides fuel economy benefits.

Using Your New Donut Knowledge

Now that you know how to decode the donut, remember that using the right motor oil goes a long way in helping:

• Lubricate and protect engine parts
• Prepare engines for extreme weather
• Reduce engine wear and friction
• Start engines up more easily

Watch those label identifiers and remember that motor oil thins when heated and thickens when cooled. So choose the right grade for your climate to get the best engine flow. And the next time you look at a container of GTX, read the label to see how much you've learned!