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What Is Multigrade Oil? (Definition, Benefits, FAQs)

November 29, 2021

Decades ago, cars only used single-grade oils, which meant that seasonal oil grade changes were necessary. 

However, advances in oil technology in the 1950s gave us the multigrade automotive engine oil, an oil that you could use all year round. 

But, what exactly is a multigrade oil?
And, what are the benefits of using one? 

In this article, we’ll try to answer these questions in detail. 
We’ll also go over the types of multigrade oils available today and answer some other FAQs you might have. 

This Article Contains: 

Let’s get started. 

What Is Multigrade Oil

Multigrade oil is an engine oil that performs equally well at a high or low temperature. It’s typically created by blending a base oil (synthetic oil or mineral oil) with an additive called the Viscosity Index Improver

As a result, a multigrade oil stays fluid at a lower temperature, but at a higher temperature, the oil doesn’t become too thin (which is something monograde oils can’t do). 

This means that the lubrication film of a multigrade doesn’t break even at the highest operating temperature. 

But, how can you know if your motor oil is multigrade or monograde oil
You can recognize a multigrade by the typical SAE J300 viscosity grade assigned to it by the Society of Automotive Engineers (SAE)

For example, let’s take 10W-30.

Here, W stands for winter SAE grade. The number before W denotes the viscosity or oil flow at 0°F. The lower this number, the better your oil will perform in winter. 

The digit after W stands for a specific viscosity grade at a higher temperature (212°F). The higher the number, the more resistant the engine oil will be to thinning at operating temperature. 

Any multigrade oil must pass the SAE viscosity grade standards to be approved for use.

Now that you know what multigrade oil is, let’s explore its benefits. 

What Are The Benefits Of Using Multigrade Oil

Here are the benefits of using multigrade oil for your gasoline or diesel engine: 

Let’s go over some multigrade oil FAQs next.

7 FAQs About Multigrade Motor Oil

Here are answers to some of the questions you may have about multigrade oils and associated topics:

1. What Are The Different Types Of Multigrade Oils?

Multigrade oils are typically available in three motor oil types: 

A. Mineral Multigrade

A mineral multigrade engine oil uses light-weight mineral oil as the base oil. 

Mineral oil (conventional motor oil), derived from crude oil, has excellent properties to provide lubrication to engine parts at high temperatures.

Oil manufacturers usually add a Viscosity Index Improver to keep the conventional motor oil fluid at low temperature and thick enough under high temperatures.

Viscosity Improvers thicken the mineral oil when the oil heats up and enables the multigrade to support more load or shear under operating conditions. 

B. Semi-Synthetic Multigrade

Oil manufacturers create a semi synthetic motor oil by mixing mineral oil (crude oil derivative) with a synthetic oil base. 

As a result, the synthetic blend offers adequate lubrication for longer and produces less acidic byproducts that may erode your engine parts.  

Another plus of semi synthetic oil is that it offers better fuel economy at lower prices than a fully synthetic blend.  

C. Fully Synthetic Multigrade

A fully synthetic motor oil is distilled, refined, and purified by oil manufacturers at a molecular level to make it ideal for any modern petrol or diesel engine. 

Since synthetic oil has a higher viscosity index than mineral oil, it’s less affected by temperature change. It requires a lesser amount of oil additive to keep the oil fluid under operating temperature. 

The better thermal stability of synthetic oil also keeps it from degrading faster than conventional oil. This lubricant has improved detergent properties, which help fight corrosion on engine parts and lower sludge formation. 

Moreover, as synthetic base oils are devoid of impurities, you can use them for motorsports and extreme climate conditions. 

A full synthetic or synthetic blend is also essential for vehicles with turbocharged engines, as these engines have a higher operating temperature than a standard engine. 

2. What Is The Most Common Multigrade Engine Oil? 

SAE5W-30 is the most widely used motor oil for light-duty gasoline and diesel engines. 

This engine oil is a lower viscosity oil, which means it stays less viscous at a low temperature than, say, a 10W-30. 

Its hot kinematic viscosity is 30, which means it stays less viscous at a higher temperature than a thicker oil like 5W-50. 

The SAE J300 5W-30 engine oil can stay fluid at temperatures as low as -22ºF and as high as 95ºF. It’s an ideal choice for gasoline or diesel car owners who experience a lot of seasonal temperature variations. 

However, you should always use a lubricant with a viscosity grade recommended by engine manufacturers to ensure a smooth running engine with fewer oil changes.

3. What is Monograde Or Single Grade Motor Oil?

A monograde or single grade oil only has one SAE viscosity grade, defined by the SAE J300 standard. It’s meant either for hot or cold applications only.

A monograde oil is also called “straight-weight” oil. 

Monogrades usually fall under two categories: 

4. Should I Use Multigrade Or Single-Grade Oil?

Multi grade oil is recommended for most modern gasoline and diesel engines. 

Here’s why: 

5. Does Multigrade Oil Improve Fuel Economy?

Using a multigrade engine oil for your gasoline or diesel engine can help you save 1.5 – 3% on fuel compared to a monograde oil. 

Since a multigrade allows lower temperature cranking and protects engine parts at high temperatures, it minimizes fuel consumption. Consequently, it offers improved fuel economy in the long run. 

6. How Does A Viscosity Index Improver Help?

A Viscosity Index Improver (VII) is an oil additive used to alter the viscosity index of motor oil. 

Note: The viscosity index is the relationship between temperature and the oil viscosity (resistance to flow). The higher the viscosity index, the lesser the viscosity changes with temperature

The Viscosity Index Improver is an organic chain molecule that dissolves in the engine oil. 

Under cold weather, this additive shrinks and bundles up, offering lesser resistance to the oil to flow. When hot, its molecules expand to provide higher resistance to the oil, increasing the oil viscosity. 

The viscosity index additive also works as a low viscosity oil under pressure. 

How?
The oil is subjected to high shear within the internal combustion engine, caused by the piston ring sliding against the cylinder wall. 

As a result, the viscosity improvers stretch out like a long thin piece of string, turning the oil into a lower viscosity oil.

In this way, the oil can still resist the high shear and doesn’t get lost as oil consumption. Also, as the oil inside is a low viscosity oil, it reduces friction, giving you better fuel economy.

7. When Is It Better To Use Single-Grade Oil? 

You can use monograde oil if you drive in scorching conditions like desert heat or constant high temperatures year-round. 

In such cases, a monograde may work better to cope with the higher ambient temperature. You can also use single grade oil as a seasonal oil for classic cars.

Then, there are exceptional cases, like lawnmowers, where it’s more economical to use single grade lubricant. 

Closing Thoughts 

Using the right multigrade oil is critical for optimizing your vehicle’s performance, of course, in addition to regular oil change and maintenance. 

And, if you’re looking for a competent and reliable car repair solution to help you with all of that, contact RepairSmith!

RepairSmith is a mobile atuo repair and maintenance service provider that offers competitive and upfront pricing on a range of car services.

Our ASE-certified mechanics will not only help you select the suitable automotive lubricant for your vehicle but can also perform the oil change and oil maintenance right in your driveway. 

Contact us to book an appointment now!