Do I have to follow oil viscosity recommendations?

When you go to get your vehicle an oil change, there’s a specific type of oil that’s recommended for your vehicle. Vehicle manufacturers tend to err on the side of safety, recommending specifics such as oil change times a little sooner than needed to account for extreme conditions. A good auto repair shop uses the right oil every time. Like using premium gas, one of the recommendations they give is the type of oil that the vehicle requires. Do you have to use 5w-30 in your car, or is it asking for 20w-50 instead? And what do these numbers even mean? For the uninitiated, this may seem like auto industry gibberish, but there are stark differences between the different kinds of oil, and while a minor variance might not be damaging, being too far off could cause irreparable damage to your engine.

What do those numbers stand for?

While many people think that the “w” stands for weight, that’s not the case. The “w” doesn’t actually indicate a unit of measurements like weight or watts; instead, it stands for Winter. Oil thins out when it heats, and thickens when cool. The first number–the winter number–represents the thickness at 0° F, while the second one represents the thickness at 212° F. The hyphen indicates that it fluctuates between that minimum and maximum with changes in temperature. 

 

Oil viscosity affects performance

Oil Viscosity ScottsdaleThe thickness of the oil depends on how easy it flows through the system. Because of this, it’s important to get it at the right level for your vehicle.

  • Oil that’s too thin won’t provide adequate lubrication for moving parts. This causes these parts to wear out more quickly and reduces engine life.
  • At one point, thicker oils were considered better by default. But oil that is too thick increases pressure, thereby increasing engine temperature.
  • Using oil that’s the wrong viscosity level can cut up to 10,000 miles or more off the life of your engine since it isn’t the optimum thickness.

When in doubt, trust the owner’s manual

In general, following the owner’s manual is your safest course of action. Your manual will also indicate other areas you may need to use specific fluids, like premium gasoline in a BMW. There are, however, exceptions to the rule. While few people have to worry about the high end of the temperature scale–the outside surroundings, at least, won’t get to 212° F–some climates experience very low temperatures. If you live in one of these climates, you may want to adjust the viscosity downwards slightly if it’s cold year round. But besides that, listening to the recommendations given by the manufacturer is usually your best option.