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5W30 vs. 10W40: What's the Difference?

Edited by Aimie Carlson || By Harlon Moss || Updated on October 4, 2023
5W30 and 10W40 are motor oil viscosity grades; 5W30 flows better in cold temperatures, while 10W40 is thicker and suited for warmer conditions.

Key Differences

5W30 and 10W40 refer to the viscosity grades of motor oils, which tell us how these oils behave at different temperatures. The numbers before the "W" represent the oil's flow at cold temperatures. In 5W30, the "5" means it has a lower viscosity and flows better when cold compared to the "10" in 10W40.
When considering the numbers after the "W," they indicate the oil's viscosity at 100°C (212°F). The higher this number, the thicker the oil remains at higher temperatures. So, 10W40 oil is thicker at high temperatures compared to 5W30, providing potentially better protection in warmer conditions. Conversely, 5W30, being thinner at high temperatures, can provide efficient lubrication without being too thick.
Given their characteristics, 5W30 oils are often recommended for colder climates or regions with more fluctuating temperatures. It offers quicker startup protection because of its superior flow when the engine is cold. 10W40, on the other hand, might be more suitable for consistently warm environments or older engines, as it maintains a thicker consistency in heat, potentially offering better wear protection.
In summary, the choice between 5W30 and 10W40 hinges on the specific needs of the engine, local climate, and manufacturer recommendations. 5W30 ensures better flow in colder temperatures, while 10W40 remains thicker in warmer conditions, potentially offering enhanced protection.

Comparison Chart

Cold Viscosity Rating

5 (Flows better when cold)
10 (Thicker when cold)

Hot Viscosity Rating

30 (Thinner at high temperatures)
40 (Thicker at high temperatures)

Suitable Climate

Cold or fluctuating temperatures
Consistently warm temperatures

Engine Age Suitability

Newer engines
Older engines or those requiring thicker oil


Provides quick startup protection due to better flow in cold temperatures
Offers potentially better wear protection in warm conditions

5W30 and 10W40 Definitions


5W30 ensures better flow when the engine is cold.
Using 5W30 can help in smoother startups on chilly mornings.


10W40 is suitable for engines that require a thicker oil at operational temperatures.
For vehicles experiencing high temperatures, 10W40 is often the go-to choice.


5W30 can offer protection during both cold startups and regular operation.
I use 5W30 for its balanced protection throughout the seasons.


10W40 provides a balance between cold flow and high-temperature protection.
To ensure my engine's protection in the summer, I switched to 10W40 oil.


5W30 provides efficient lubrication at high temperatures without being overly thick.
For efficient engine performance, my newer vehicle uses 5W30 oil.


10W40 maintains a thicker consistency at high temperatures, offering potential wear protection.
My older vehicle benefits from the added protection of 10W40 oil.


5W30 is commonly recommended for most modern vehicles.
The manufacturer's manual suggests using 5W30 for optimal performance.


10W40 is a motor oil viscosity grade tailored for warmer climates or older engines.
Given the tropical climate here, 10W40 oil is ideal for my car.


5W30 is a motor oil viscosity grade suitable for cold or fluctuating temperatures.
My mechanic recommended 5W30 oil for my car due to the region's cold winters.


10W40 might be preferred in regions with consistent warmth or for engines under heavy load.
For my truck that frequently hauls heavy loads, I trust 10W40 for optimal protection.


What do 5W30 and 10W40 represent?

Both 5W30 and 10W40 are viscosity grades of motor oils, indicating their flow characteristics at different temperatures.

Which oil flows better in cold temperatures?

5W30 flows better in cold temperatures compared to 10W40.

Where might one ideally use 5W30?

5W30 is ideal for colder climates or regions with fluctuating temperatures.

Which oil might improve fuel efficiency?

5W30, being thinner, might offer slight improvements in fuel efficiency over 10W40 in certain conditions.

What's the significance of the "W" in 5W30 and 10W40?

The "W" stands for "Winter," indicating the oil's flow properties at cold temperatures.

Is 10W40 thicker at higher operational temperatures?

Yes, 10W40 is thicker at high temperatures compared to 5W30.

Why might one choose 10W40 over 5W30?

10W40 is suitable for consistently warm environments, older engines, or when thicker oil is required.

Can I use 5W30 in a tropical climate?

While you can use 5W30 in a tropical climate, 10W40 might offer better protection due to its thicker consistency in heat.

How does 5W30 benefit cold startups?

5W30 ensures quicker engine protection at startups due to its superior flow in cold conditions.

Can 10W40 be used year-round?

10W40 can be used year-round, especially in regions with consistent warmth or in vehicles that benefit from its properties.

Which oil might be recommended for most modern cars?

Most modern vehicles are often recommended to use 5W30.

How does 10W40 protect older engines?

10W40, being thicker at operational temperatures, can offer better wear protection, beneficial for older engines.

Which oil might reduce startup wear in cold climates?

5W30, with its better flow in cold temperatures, can reduce startup wear in colder climates.

How often should I change 5W30 or 10W40 oil?

Change intervals can vary based on the oil type (synthetic or conventional) and manufacturer recommendations.

Are 5W30 and 10W40 synthetic oils?

Both 5W30 and 10W40 can be found in synthetic, semi-synthetic, and conventional forms.

Is it okay to switch between 5W30 and 10W40?

It's essential to follow the manufacturer's recommendations, but occasional switches, especially with similar base oils, may be okay.

Why is viscosity important in motor oils?

Viscosity determines how well an oil flows and protects the engine under different conditions, which is vital for 5W30 and 10W40.

Does 5W30 offer protection at high temperatures?

Yes, 5W30 provides efficient lubrication at high temperatures, although it's thinner compared to 10W40.

Can 5W30 handle heavy loads?

While 5W30 can handle regular vehicle loads, for consistently heavy loads, a thicker oil like 10W40 might be more appropriate.

Can I mix 5W30 and 10W40 in my engine?

Mixing different oils is not recommended. Always consult the vehicle's manual and ideally use the recommended grade.
About Author
Written by
Harlon Moss
Harlon is a seasoned quality moderator and accomplished content writer for Difference Wiki. An alumnus of the prestigious University of California, he earned his degree in Computer Science. Leveraging his academic background, Harlon brings a meticulous and informed perspective to his work, ensuring content accuracy and excellence.
Edited by
Aimie Carlson
Aimie Carlson, holding a master's degree in English literature, is a fervent English language enthusiast. She lends her writing talents to Difference Wiki, a prominent website that specializes in comparisons, offering readers insightful analyses that both captivate and inform.

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