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Javaughn Barrow

Engine Oil Viscosity Grades; Need To Know Basics

One crucial part of vehicle ownership is engine maintenance. Oil changes are key to an engine maintenance schedule and a great way to protect your engine’s components. Ever heard of the phrase, “A well oiled machine” ? That’s because a well oiled machine such as your engine, works best when it is properly lubricated. Proper lubrication of your engine can increase the engine’s longevity. Proper lubrication means you have the right engine oil viscosity.

Excuse me for stating the obvious, but engine oils are liquids. Liquids tend to have their state change depending on the temperature. When their state changes, it also changes how it flows when being moved. It can move very slow at times or quickly depending on the temperature. This rate of flow in different temperatures is referred to as the liquid’s viscosity. So when we are talking about engine oil viscosity, we are referring to its rate of flow through an engine’s lubrication system, at different temperatures.

What you will learn :

What do oil viscosity numbers mean?

Oil Viscosity numbers indicate the engine oil grade. The oil grade indicates the oil’s activity of thickness or thinness during certain temperature changes. There are multigrade engine oils and then there are monograde engine oils. Multigrade engine oils are able to act like two different weights of oils for cold and hot temperatures. This is true liquid engineering. Viscosity modifiers are added to these engine oils making them multigrade engine oils. These modifiers help its state when things are either cold or hot.

It especially helps when things get hot because oils get burned off and evaporate. However, for example, Mobil 1 Full Synthetic engine oils have passed through extensive heat testing to ensure when the oil starts acting as a thicker grade oil, not much is burned off. These engine oils have an industry standard evaporation test called the ILSAC GF-6A. This is a test, in which the oil passes because no more than 15% of its mass was burned off after heat testing. Some engine oils have a GM Dexos 1 rating, which has even stricter standards, with no more than 13% can be burned off.

Examples of multigrade engine oils are :

• 0W-20
• 5W-20
• 5W-30
• 10W-30
• 0W-40
• 10W-40
• 15W-50
• 20W-50

These numbers indicate what the oil’s activity is like at certain temperatures. The number along with the “W” (Winter) represents the oil’s viscosity when it is in cold temperatures. The second number represents the oil’s viscosity when temperatures are getting heated. As per the first example, the 0W-20 means this particular oil acts as an SAE 0 grade oil when cold. It also acts as an SAE 20 grade oil when it’s getting heated. It doesn’t mean the weight of the oil changes between both, it just means it acts like it. SAE is an international standard for ranking oil weights. Society of Automotive Engineers (SAE) focuses on developing automotive standards.

Examples of Monograde engine oils are :

• SAE 30
• SAE 40
• SAE 50
• SAE 10W

Monograde engine oils are like multigrade engine oils, except they are only validated at either hot or cold temperatures, not both. Mostly hot. Most monograde applications are with racing cars and heavy duty truck applications. These types of oils are usually best in very hot temperatures.

Is it ok to change oil viscosity?

First off, it’s always important to use what the car manufacturer recommends for your specific model. That being said, some car manufacturers recommend different oil grades depending on what time of year it is. They use this seasonal approach to gauge the temperature of the environment and the conditions the engine oil may be seeing. They may recommend a thinner grade oil in the winter (less viscous) and a thicker grade oil in the summer (more viscous). However, let’s say your car was validated and tested on a 5W-30 engine oil for example.

Then you put a thicker grade engine oil such as a 10W-30. It wouldn’t be great. The engine is now experiencing a thicker engine oil especially on start up. It would be harder for that oil to pass through the engine’s lubrication system. Timing is everything in an engine, so if oil isn’t where it’s supposed to be at a certain time, you risk engine damage. However, if your engine manufacturer recommends a 10W-30 engine oil and you put a 5W-30 oil in it, that’s not as bad. Simply because the 5w30 falls within the 10w30’s range. The 10w30 engine can deal with the thickness of an SAE 10W oil, so if you put the SAE 5W it should only make the process easier. That being said, it’s best to stick with the manufacturer’s recommendation.

What is the best viscosity for motor oil?

There is a trend of motor oils getting thinner grades as time goes on. Technology gets better, engine design and materials get improved. This allows for engine oils companies to use thinner grades with great benefit. The best viscosity for an engine oil, is summed up into a couple characteristics. One is to allow engine components to operate with the least amount of resistance. The other is to simultaneously protect said engine components from wear.

Engine oil has gone from the common 5W-30 to 5W-20 to 0W-20 to even now 0W-16 engine oils. The most common engine oils are the 5W-30 and 5W-20, with 0W-20 rapidly growing. These oil grades getting thinner accomplishes both characteristics, of the engine components moving with less resistance while still being able to protect against wear. Thanks to engine advancements and engine oil companies efforts, this can be accomplished.

What happens if I use a higher-viscosity engine oil?

When an engine is in development it is tested and validated on a specific engine oil. This engine oil is the manufacturer’s recommendation for what type of engine oil you should use. However, it’s just a recommendation. One you should also take seriously. That being said, let’s say you want to put a different oil than recommended. You should be aware of the risk you take with your engine’s components. In this case, where you want to go with a thicker oil grade (higher viscosity) than your manufacturer recommends, it won’t be great.

A thicker oil can put more resistance on the engine’s components, making it harder than usual to operate. You may have a decrease in fuel economy and power. Instances where one might opt in for a higher engine oil viscosity, is if your engine is going to see higher temperatures. Maybe you’re taking your car to track for racing, or you have a utility vehicle that is going to be more of a workhorse and experience more load.

Is a higher-viscosity oil better?

Higher viscosity engine oils means that the engine oils are thicker. Thicker engine oils are better for warmer/hotter temperatures in engines. Liquids evaporate when heat is applied. Engine oil is no different. However, for engine oils, especially multi grade engine oils, evaporation happens at a very slow rate. Thicker grade engine oils have better protection for your engine’s components at higher temperatures. This is the very reason synthetic engine oils add viscosity modifiers to the mix, so the oil can act like a thicker grade oil.

This in turn better protects engines at extreme heat. However, thicker grade engine oils can cause your engine components to experience more resistance in cold temperatures. You can run into cold cranking engine issues if so. In cold temperature scenarios, a thinner oil has a better rate of flow for your engine. Multigrade engine oils are the solution for these issues, being that they are validated for both hot and cold temperatures.

Engines that experience a higher than normal temperature and heavier loads, usually use thicker grade (higher viscosity) engine oils. Here are a few scenarios that may use thicker grade engine oils: 

• Race cars
• track cars
• sports cars
• 1950’s and older cars
• Mining/construction equipment 

Is a thicker oil better for older engines?

Engine oils today are moving in a direction of getting thinner and thinner. This is due to the fact that engine design, technology and engine materials have gotten better over time. So much so that modern cars have been using thinner engine oils than a 5W-30, like 5W-20, 0W-20 and even 0W-16 engine oils. These thinner oils are still able to protect modern engines against wear because of better materials used for engine components. However, older engines were designed differently and may have wider passage ways for the oils to pass through.

Thinner oils might not be the right choice for such a design, because the engine needs oil pressure for proper engine oil circulation. This is where thicker grade oils play a better role in these scenarios. Thicker engine oils are also less viscous, which means they don’t thin out as much when temperatures rise. Older engines tend to experience higher temperatures, hence using a thicker grade engine oil would be optimal. Also older engine materials are not as great as modern engines, so a thicker grade engine oil is yet again is better for these types of engines (1950’s & older). 

Thicker oil than 5w-30?

5W-30 engine oils are one of the most common today. A thicker oil can be a multigrade oil or a monograde engine oil. This 5W-30 is an example of a multigrade engine oil because of the two number representations. The “5W” represents the oil’s viscosity in cold temperatures. The “W” stands for winter, hence the first number being the cold representation. The second number “30” represents the Hot rating. This means the oil acts like an SAE 30 grade oil when things heat up. There are oils with singular ratings, representing one temperature range, called monograde engine oils unlike the multigrade oil. Thicker engine oils than 5W-30, would simply mean that either the first or second number is higher. As for monograde engine oils, the rating would just have to be higher than “SAE 30”. Here are a few examples of thicker multigrade and monograde oils than 5W-30:

Multigrade: 

• 10W-30
• 0W-40
• 10W-40
• 15W-50
• 20W-50

Monograde: 

• SAE 40
• SAE 50

Is Synthetic oil higher viscosity?

When something is high in viscosity, it means that the characteristics of the liquid doesn’t change much when temperatures change. It’s essentially the liquid’s thickness, like the difference between water and pancake syrup. In the case of engine oils, the thicker an oil at high temperatures means it does not thin out too much and can still protect the engine against wear.

Synthetic engine oil viscosity does the best job at engine protection than conventional engine oil viscosities. The base oil of a synthetic, has more stable molecules which prevents it from being more inconsistent as temperature changes. So the base oil of a synthetic makes it higher in viscosity. Conventional oils for instance, have molecules with different sizes, shapes and weight. So when things heat up, the smaller molecules are more susceptible and get burned off quicker. This reaction causes the oil to thin out more as temperatures rise.

Conclusion

Engine oil companies go through quite a bit of testing to ensure their oil can deliver maximum protection. Protection whether your car is new, old, high mileage or low mileage. Because of this liquid engineering, rest assured there is oil out there for your engine. The best way to give your engine what it needs, is to confirm in the owner’s manual or manufacturer recommendations of what oil grade your engine uses and the oil change interval. Oil Changes still remain one of the key ways to protect your engine’s components so they can last. A happy engine is a lubricated one.

Javaughn Barrow

Hello! My name is Javaughn Barrow, a young car enthusiast who writes all the articles for Karcandy.com. I’ve written over 50 articles about automobiles. With each article, I deepen my understanding and expertise in writing and the automotive world. Ever since childhood, I’ve always had a strong passion for cars. All types shapes and sizes were interesting to me. I’d spend most of my time after school researching cars and the more I found out about them the more exciting it was. In my teens, I created a fan page about corvettes posting content at least ten times a day! Yes, I was crazy about it. The page ended up garnering over 40k followers! After a while, I wanted more than a fan page. I wanted to express my passion differently. I wanted to create more helpful content, higher-quality content. My first car was a 2013 VW CC Sport. Learned very quickly car ownership wasn’t as expected. I spent a lot of time replacing control arms, cam position sensors, brake rotors, brake pads, etc. Walking away with more information than I knew before. As I was growing in my automotive journey I was learning about writing. Starting by writing a detailed outline about 300 words long then I would pay a professional to write a full 1000-word article and learn from them getting familiar with the process of writing. The moment I realized I could use my writing skills to express my passion for cars and help people simultaneously, I started Karcandy.com. I realized with my unique perspective coupled with my hard work discipline and work ethic I can create a space online to help bridge the gap between the complicated and simple in the automotive world. I’m motivated by the challenges and work it will take to create such a space. My work ethic is something I choose to refine and make better each day. I think it’s important to push myself and stay committed to my evolution as a human and this website is only one of the results of that.

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