What is with all these oil options?

Ever look at all the motor oil on the shelf and wonder what the numbers mean or what all the differences are?

Well here are some answers.

First….viscosity. Viscosity is a measurement of flow. In this case, how fast the oil will flow at 100 degrees Centigrade. Sometimes this term is translated to thick. How thick the oil is. A crude but usable definition.

So the 2nd number in any motor oil is the viscosity of the oil. A 5W20 oil is thinner than a 5w30 oil.

Why this is important is the engines are designed to have a certain amount of flow at certain temperatures. If too thick an oil is used then your gas mileage will suffer (thicker is harder to push), and the oil will not last as long as it should.

If the oil is too thin it may not pick up enough heat as it courses through your engine and the oil pressure may drop below what the engine needs.

The 1st number is a measurement of the oil’s pumpability at cold tempuratures. In other words a 10w30 will not be any good at temperatures below -20 degrees Fahrenheit. A 5w-30 oil will be fine down to about -30 degrees Fahrenheit and 0w-30 can go all the way to -40 degrees Fahrenheit.  Of course out here in New Mexico we rarely go below 0 degrees so it really does not matter that much here.

Now that we have covered viscosity and pumpability let’s talk about those two little letter to the right of the api viscosity indicator.

Modern gasoline engines require different additive packages than modern diesel oils. To that end the first letter (in this case an “S” is for gasoline. Oil designed for diesel applications begin with a “C“.

The second letter is for whatever year range the oil is designed for. For instance an SA oil is an oil designed for a gasoline engine built in the 1920s. Try to put this oil in your 2012 whatever and the engine will not be long for this world.

Today’s rating is now “M“. So a motor oil sold on the shelf today for gasoline engines, should have a rating of “SM“. If you find an oil for sale that has a SL rating it was designed for cars a few years ago. Now modern oils are perfectly fine for older applications. No problems there.

So what kind of oil and viscosity do you need?

That answer is specific to the manufacturer that created your car. I can tell you that most vehicles on the road today use a 30 weight oil. Either 10w30 or 5w30 depending on how cold it gets.

Some vehicles require a thinner oil. Many Fords and Hondas especially need 5w20 oils. Usually the viscosity requirement is on the oil fill cap under the hood. If not there find it in the owners manual or call us. We can tell you.

Very few vehicles on the market today require synthetic oil but a few do. Mostly your higher end sports cars and/or European cars. If your vehicles manufacturer requires synthetic oil I would high recommend you follow that. True, you could put cheaper dino oil in it but by 80 or 90k miles the engine will be sludged up and worn out.

To sum up … the 1st number is an indicator of pumpability at cold tempuratures. The 2nd number is the oils viscosity or how well it flows at 100 degrees centigrade. Hope this helps. We will be talking about other factors in choosing an oil or oil change service all month so stay tuned.