It can be very easy to get confused standing in front of the oil shelf at the local auto parts store. There are so many types, brands, and grades of oil. How do you know what you're getting and what you should use in your engine? It isn't as hard as it seems, though. There are a few things to consider but you can decode the mystery of which oils fits your needs.

Understanding The Numbers

How are you supposed to know the difference better oils when they all have numbers that don't seem to mean much. Come on, what does 10w30 really mean? It is not really as technical as you might think. The number on the bottle is the SAE viscosity rating or thickness of the oil. For instance, a 5w30 is thinner than a 10w30 because it has a lower viscosity. The "w" in the name indicates winter use and the 30 is the SAE equivalent. Basically, it means that the oil cold has the properties and viscosity (or thickness) of an SAE 5 weight oil. But when it warms to 210 degrees it has the properties of an SAE30 weight oil. The same is true of a 10W30 or 10W40 but keep in mind, the smaller the number, the thinner the oil. This is why in the cold weather, a 5W30 offers better cold start lubrications than a 20W50 would.

What Oil Should I Use?

Most engine manufacturers will specify an oil for the engine they offer but there are times when changing that is okay. Check your owner's manual for the oil specification and to see if there is an alternative. It is common for a truck manufacturer to specify a 10W40 in the summer with an alternative 10W30 or ever a 5W30 in the winter months. In very warm climates, the specifications will often be a single number. For Instance, SAE30 might be all that is indicated. Because there is no concern for the cold weather start up, the first number becomes irrelevant. So Stick to the recommended oil or an equivalent viscosity if at all possible.

What If I Can't Get The Correct Oil?

If you find yourself in a position where the engine is low on oil and you can't get the specific oil where you are at, you can substitute another oil with a similar viscosity. The difference between SAE 30 and 40 is very slight and having a slightly heavier oil in the crankcase is better than running it low and damaging the engine, bearings, and other internal components.

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