What Does Your Motor Oil’s Reading Grade Mean?

 

Motor oil is an essential fluid for your car, as it keeps all the parts lubricated and helps to keep your engine running smoothly. The grade of that is an indicator of its performance under stressful conditions, but car owners don't usually know much about that.

 

Let's discuss what each grade means and how it can impact your car's performance.

 

How are Motor Oils Graded?

 

Motor oil is graded on a numerical scale, with higher numbers indicating better quality. The lower the number, the poorer the quality of the oil. This system has been in place since 1936, when it was introduced by American Petroleum Institute (API).

 

API created this standard to help consumers understand the various properties of motor oils and make an informed decision when purchasing one. The reading grade of motor oil measures its ability to resist shearing or break down under pressure. The higher the reading grade, the more resistant the oil is to shearing.

 

Lubricants are graded according to their viscosity index (VI), with a higher VI indicating more excellent resistance to shearing. Many factors affect the quality of oil, including its composition and source. However, the VI is a standardized measure, and all lubricants are graded against it.

 

Motor oils with higher VI ratings are more expensive than those with lower ones because they require more additives and base stocks, which increase their cost. However, these motor oils have better lubrication properties and can help protect your engine from wear.

 

Most Common Oil Grades

 

SAE (Society of Automotive Engineers) classifies engine oils according to their viscosity at different temperatures. It included cold and hot conditions and the shear stress range over which they effectively protect against wear under extreme loading conditions such as racing or off-road use.

 

The three most common ratings for motor oil are SAE 0W-30, SAE 0W-40, and SAE 20W-50.

 

1. SAE 0W-30 is the lightest weight oil and will offer the best fuel economy. It's also the most susceptible to shearing, so it's unsuitable for high-performance engines or vehicles that frequently tow heavy loads.

 

2. SAE 0W-40 is an excellent all-around choice for most vehicles. It has a higher VI than SAE 0W-30, making it less susceptible to shearing.

 

3. SAE 20W-50 is the heaviest weight oil and is best suited for high-performance engines or vehicles that frequently tow heavy loads. It has a lower VI than SAE 0W-40, making it more resistant to shearing. It is an excellent choice for hot climates or high-performance engines.

 

All of this might not seem very clear if you're not familiar with motor oil grades, so it's best to take expert advice rather than doubting your choice of motor oil at the pump. So come to our service center in North Attleboro, Massachusetts, and let Patriot Subaru take a look at your car.