Can You Mix 5W20 and 10W30 Motor Oil? Yes, But Read This First

You often face a dilemma regarding which oil to use, whether mixing oil brands, oil types, or weight. This is especially true if you have a new car that needs 5W20 oil, but only the more expensive 10W30 is available in the garage or store. In our previous article, we tackled mixing 5W20 with 5W30.

Can You Mix 5W20 and 10W30

Not everyone knows this, but you can mix 5W20 and 10W30. But is this something you need to do? What consequences will it have for your car? And is it a good idea in general? Keep reading if you’re interested in finding the answers to these questions.

Can you mix 5W20 and 10W30 engine oil?

Yes, you can safely mix 5W20 and 10W30 engine oil. In most cases, combining two oils with different viscosities won’t harm your engine and is better than running low on oil. However, we do not recommend doing it because every engine requires different oil viscosity to function efficiently at temperatures.

Still, the safest way to do this is to use the recommended engine oil for your car. If your vehicle is already low in oil, you should add the recommended oil first, followed by a different one. This way, you’ll be sure your engine won’t get damaged due to lack of oil.

What is the meaning of code in motor oils?

The resistance to the flow of oil is a measure of its viscosity. The Society of Automotive Engineers designates two viscosity grades for multi-grade oil. Let’s decode what 5W20 grade means. The first grade 5W is suffixed with W, meaning Winter or cold-start viscosity, at a lower temperature.

For example, when an engine starts, the oil acts with a viscosity of 5 when it is cold. The second number, 20, is determined by how the oil flows at typical engine operating temperatures. It means that 5W20 oil acts with a viscosity of 20 when the engine is hot.

Let’s compare different multi-grade oils using what we have learned above. At startup temperatures, a 5W-20 will flow more readily than a 10W-30. While at running temperatures for a typical engine, a 10W-30 will flow more easily than a 10W-40.

The viscosity of the engine oil is crucial. Engine oils naturally get thinner during heating and thicken during cooling. Engine components are better protected at low temperatures by thin, low-viscosity lubricants. In general, thick, high viscosity lubricants keep film strength better to safeguard engines at high temperatures.

meaning of code in motor oils
Overview of common SAE classes according to defined parameters

What is the difference between 5W20 and 10W30, and which is better? 

Unlike using 10w30 instead of 5w30, 10W30 and 5W20 engine oils have different viscosity for ambient and operating temperatures. In general, the 10W30 is thicker than the 5W20, making it beneficial to high mileage or older engines. However, since 5W20 oil is thinner, it flows better in ambient and operating temperatures than 10W30.

So, in a nutshell:

  • 10W30 is thicker and provides more protection
  • 5W20 is thinner and flows easily in cold and hot temperatures

In reality, the difference in weight of these two oils is only 8.7%, which is not really significant. Although 10W30 is thicker, they will function almost the same at both ambient and operating or high temperatures. However, since 10w30 tends to thicken in cold climates, technically, 5W20 is better under these conditions.

We still recommend considering the engine oil’s intended use and the environment in which the vehicle will be used before making your choice. Although both engine oils are multi-grade, 5W20 thins out enough when utilized in a place where the temperatures are relatively low. Due to this, it outperforms 10W30 in the cold. 

On the other hand, 10W30 flows well in hotter climates or throughout the summer. 5w20 is more lubricant-efficient than 10W30. While 10W30 works best for automobiles with heavy loads and commercial vehicles, 5W20 is ideal for light-duty petrol, diesel engines, and passenger cars.

Can I use 5W20 instead of 10W30 in summer?

Yes, you can use 5W20 instead of 10W30 in the summer if that’s the only engine oil you have, but using 10W30 is preferred because it performs well in warm environments. Unlike 5W20, it does not thin down fast when exposed to heat. Therefore, the engine components are better overall when using 10W30 at operational temperatures. 

Whereas in cooler climates, you can use 5W20. As it moves swiftly and smoothly to deeper engine components with less friction, it makes it possible for a vehicle’s engine to start up rapidly. It immediately lubricates engine components.

Is 5W20 better for a high mileage engine than 10W30?

When an older, high-mileage passenger car is getting close to or has reached 100,000 miles, it is advised to switch to a thicker viscosity oil, like 10W30. It can adequately lubricate the engine for preservation and even have healing properties for engine parts. Most 10W30 oils are used in diesel engines, and experts strongly advise it for heavy-duty and high-mileage vehicles.

You can barely expect anything better than 5W20 engine oil for motors with greater mileage. Due to the high mileage, the engine chamber generates more heat, which allows the oil to operate flawlessly in cold engines. 


The remarkable healing characteristics of 10W30, which is thicker and heavier, safeguard older engines. Comparatively speaking, multi-grade oil 5W20 is thinner and ideal for rapid ignitions at colder temperatures. You should only use the manufacturer-recommended motor oil in your car to keep it in top condition.

Engine oil is probably the most crucial aspect of vehicle maintenance you should keep your eye on. Follow our Facebook page to learn about car repair and maintenance tips.

Elevate your car maintenance game by reading our comprehensive guide on engine oil. Learn everything from the basics of oil types, to how to properly maintain and change it. Keep your vehicle running at its best, read our guide now!

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