5w30 vs. 10w40 — What's the Difference?
By Tayyaba Rehman — Published on December 24, 2023
5w30 and 10w40 are motor oil viscosity grades; 5w30 is thinner at low temperatures than 10w40, but 10w40 is thicker at high temperatures than 5w30.
Difference Between 5w30 and 10w40
Table of Contents
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Key Differences
5w30 and 10w40 represent specific viscosity grades of motor oils. The "W" stands for winter, indicating the oil's performance at colder temperatures. For 5w30, the '5' signifies that it's more fluid at lower temperatures compared to the '10' in 10w40. This means 5w30 offers better cold-start protection than 10w40.
On the flip side, the second number represents the oil's viscosity at 100°C (212°F). Here, the '30' in 5w30 denotes that the oil is thinner at high temperatures compared to the '40' in 10w40. Therefore, 10w40 offers more protection at elevated temperatures, ensuring better lubrication when the engine is hot.
Choosing between 5w30 and 10w40 often comes down to the specific needs of a vehicle and the climatic conditions of the area. For instance, in colder regions, the quick flow of 5w30 can be more advantageous, ensuring rapid engine protection during cold starts. In contrast, areas that experience high temperatures might benefit from the thicker consistency of 10w40, which provides enhanced protection in hot conditions.
Another key difference is their application. While 5w30 is commonly recommended for newer vehicles due to its fuel efficiency benefits, 10w40 is often chosen for older vehicles that might need a thicker oil to maintain proper lubrication. This isn't a hard and fast rule but rather a general observation in automotive practices.
Lastly, while both 5w30 and 10w40 can serve a vehicle effectively, it's imperative to refer to the manufacturer's recommendation. Following the vehicle manual ensures optimal engine performance and longevity, regardless of whether one chooses 5w30 or 10w40.
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Comparison Chart
Low-Temperature Viscosity
Thinner (flows more easily)
Thicker (flows less easily)
High-Temperature Viscosity
Thinner
Thicker
Best Used In
Colder climates & newer vehicles
Hotter climates & older vehicles
Protection
Better cold-start protection
Better protection at high temperatures
Fuel Efficiency
Typically offers better fuel efficiency
Might be less fuel-efficient than 5w30
Compare with Definitions
5w30
Thinner at high temperatures.
At 100°C, 5w30 is less viscous than some other oils.
10w40
Less fluid than 5w30 at 100°C.
When both are heated, 10w40 remains thicker than 5w30.
5w30
Offers better cold-start protection.
In colder climates, 5w30 ensures the engine starts smoothly.
10w40
A specific viscosity grade for motor oils.
For my vintage car, I stick to 10w40 oil.
5w30
A motor oil viscosity grade.
I use 5w30 for my car as it's recommended in the manual.
10w40
Offers superior protection at high temperatures.
During summers, 10w40 keeps the engine well-lubricated.
5w30
Provides better fuel efficiency.
Opting for 5w30 might improve your vehicle's miles per gallon.
10w40
Thicker at colder temperatures.
10w40 doesn't flow as easily as 5w30 during winter starts.
5w30
Commonly recommended for newer vehicles.
Most modern cars prefer 5w30 due to its fuel efficiency.
10w40
Often chosen for older vehicles.
Mechanics recommend 10w40 for some of the older models.
Common Curiosities
Which oil provides better fuel efficiency?
5w30 typically offers better fuel efficiency due to its thinner viscosity.
What do 5w30 and 10w40 represent?
They are motor oil viscosity grades indicating performance at different temperatures.
Can I switch between 5w30 and 10w40?
It's best to follow the vehicle's manual, but occasional switches, if done properly, are generally safe.
How does the 'W' in the grades matter?
The 'W' stands for winter, indicating performance at cold temperatures.
When should I use 10w40?
10w40 is suitable for hotter conditions and often for older vehicles.
Is 5w30 suitable for older vehicles?
While it can be used, older vehicles might sometimes benefit more from the thicker 10w40.
Is 5w30 better for colder climates?
Yes, 5w30 is designed to flow more easily at lower temperatures.
Do these oil grades affect engine longevity?
Proper viscosity ensures optimal lubrication, potentially enhancing engine lifespan.
How often should I change these oils?
Oil change intervals should be based on the vehicle's manual and driving conditions.
Which oil is more popular?
Popularity varies based on vehicle recommendations and regional climates.
Is 10w40 thicker than 5w30 at all temperatures?
No, 10w40 is thicker at high temperatures, but 5w30 flows more easily at cold temperatures.
Are these oils compatible with all engines?
Most engines will work with either, but always refer to the vehicle's manual for specific recommendations.
Are there synthetic versions of these oils?
Yes, both 5w30 and 10w40 are available in conventional and synthetic forms.
Which oil is better for high-performance vehicles?
Both can be used, but it largely depends on the manufacturer's recommendation.
Can mixing the two oils harm my engine?
While not ideal, a one-time mix in emergencies won't typically cause immediate damage. Still, it's best avoided.
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Written by
Tayyaba RehmanTayyaba Rehman is a distinguished writer, currently serving as a primary contributor to askdifference.com. As a researcher in semantics and etymology, Tayyaba's passion for the complexity of languages and their distinctions has found a perfect home on the platform. Tayyaba delves into the intricacies of language, distinguishing between commonly confused words and phrases, thereby providing clarity for readers worldwide.
