Over the weekend, we changed the oil in one of our family vehicles. This site is all about learning, and oil changes are a basic skill that we believe that any car owner/operator should learn, even if they don’t always use it – it’s certainly been a while since I’ve changed oil myself. Other basic motorist skills would include changing a tire and jump starting a vehicle. Even if you don’t change your own oil, you might find yourself needing to add oil between changes, and you will want to make sure you use the right stuff.
Of course before we get to the why or how of oil and oil changes, we must first address the what: What do the numbers on a bottle of motor oil mean? More basically, what is motor oil?
I turned to Edmunds.com to quickly answer both questions:
What is motor oil?
Most simply put, motor oil consists of a base oil and an additive pack. The base oil might be mineral (from the earth) or synthetic (from the lab). The additive pack contains detergents, agents to allow viscosity to more easily change, anti-wear agents, and more.
What do the numbers mean?
The numbers, while not the actual viscosity (resistance to flow) of the oil, indicate the grade or a representation of the viscosity of an oil. For example, our Ford uses 5W-20, a multi-grade oil (generally, modern vehicles use multi-grade oils). The number before the W (5 in my example) represents the grade of the oil at cold (or start-up) temperatures, while the second number (20 in my example) represents the grade at operating temperature.
Here, we are just scratching the surface of understanding motor oil. For a more in-depth education, in layman’s terms, visit Motor Oil University over at BobIsTheOilGuy.com.