The Importance of Oil Viscosity

February 28, 2017 4:23 pm Published by

synthetic oil changeWhen vehicle owners come to us for a Signature Service® oil change, they often ask about the number and letter combination on motor oil labels. It’s a logical question; the right oil is necessary for your vehicle’s health, so it’s important to know the exact type of oil your vehicle requires. In this article, we’ll break the code and explain what oil viscosity means for a healthy engine.


Motor Oil Properties

What do we mean when we talk about oil viscosity grades? 

The first step to answer this question is to define “viscous.” Here’s the dictionary definition: Viscous – adjective: of a glutinous nature or consistency; sticky; thick; adhesive.

So, a motor oil has a high viscosity if it’s thick and sticky. If it’s thin and flows easily, it has a low viscosity.

The second step is to understand that today’s motor oil is a multi-weight oil, which means it has different weights at different temperatures. This is a good thing; vehicles need low viscosity oil to flow during a cold start. They also need oil to maintain viscosity (not get too thin) when the engine heats up to operating temperature.

The third step is to understand oil companies can engineer motor oils to different levels of performance. Rated by the Society of Automotive Engineers (SAE), these oils maintain different viscosities at cold and maximum temperatures.


The Oil Viscosity Grades

A typical oil viscosity grade looks like this: 10W-40.

The “W” in the grade stands for winter. The number in front of the W indicates the speed with which the oil can flow at 0 degrees °F. The lower the number means the oil flows faster. As an example, 0W oil can flow faster than 5W at low temperatures.

The second number details the oil’s viscosity at the standard operating temperature of 212 degrees °F. The same rule applies here: the lower the number, the faster the oil will flow. Therefore, an oil with 20 as the second number will be thinner at 212 degrees than an oil rated with a 40.


What Oil Viscosity Means for an Engine

When you turn the ignition on, thousands of moving metal parts come to life at once. If the oil is too thick to flow through the joints, bearings, and rotating shafts, the engine dry-runs for too long. This can cause decreased fuel economy, higher engine loads, and eventually shortened engine life.

After the vehicle has warmed up, the engine oil needs to maintain its ability to lubricate properly in the face of extremely hot temperatures. If the viscosity grade is too low, mechanical wear sets in as all the metal pieces grind together. This also results in shortened engine life.


What Oil Viscosity Means for Drivers

For every vehicle produced, the manufacturer specifies the required viscosity grade (or range of grades) in the owner’s manual. These specifications are crucial as they ensure the proper function of your engine. If you use a different grade for too long, you may void your warranty.

There are some cases, however, when using a different grade is unavoidable. For example, an emergency situation may arise when your 5W-30 oil gets low and you only have access to 10W-40. If this is the case, running on the wrong oil is preferable to running on no oil at all. If this happens to you, just be sure to get your oil changed as fast as possible.


Jiffy Lube® Is Your Local Oil Change Expert

As we’ve shown, using the properly graded oil is a “must.” Yet beyond the oil viscosity grade, there are several attributes that differentiate motor oils. Producers use additives such as detergents, anti-wear agents, friction modifiers, and rust/corrosion inhibitors to improve the ability of the oil to minimize sludge and stay effective longer.

For drivers in greater Sacramento and the Central Valleys, this means you have a variety of choice of motor oils of the same viscosity grade! When you come to us for a Signature Service® oil change, we’ll explain the different options available. This way, you can pick the best option for your wallet and your vehicle, and get the peace of mind knowing that your vehicle is well maintained.


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