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20w40 Vs. 20w50: Which Motor Oil Should You Choose?

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Hi, I'm Azim Uddin, a student who loves cars. Visit to learn about car maintenance for beginners and experts. In my studies, I found a cool connection between hosting and car care. Join me on this journey where every road has a story, and hospitality meets the thrill of cars. Explore, learn, and enjoy the ride with me!

Last Updated on May 10, 2024 by Azim Uddin

When it comes to selecting the best motor oil for your vehicle, the options can be overwhelming. The choice between 20w40 and 20w50 motor oils is a common dilemma for many vehicle owners.

So, what is the difference between 20w40 vs. 20w50? The 20w50 has a higher viscosity in warmer temperatures, making it suitable for high-performance engines. It is also efficient in older engines that require extra friction cushioning. Conversely, the 20w40 has a slightly lower viscosity in warmer temperatures and is best suited for standard engines.

This comprehensive guide will break down the differences between 20w40 and 20w50 motor oils. This will help you make an informed decision for your beloved vehicle.

Comparison Table: 20w40 vs. 20w50

Before we dive deep into the specifics, let’s start with a quick side-by-side comparison to give you an at-a-glance overview of 20w40 and 20w50 motor oils.

ViscosityLess viscous in hot temperaturesMore viscous in hot temperatures
Hot Weather PerformanceLess suitable for very hot conditionsEffective in extreme heat
Flash Point200°C267°C
Pour Point-30°C-30°C
Fuel EconomyMore Fuel-EfficientSlightly Less Fuel-Efficient
Price (per 1L)$381$445
Where to UseLong-distance driving: it is more fuel-efficientGasoline and Diesel Engines (Moderate to Large), High-Performance Motorcycles, Aviation Vehicles, Older Vehicles

Overview Of 20w40 And 20w50

20w40 vs 20w50

Here is an analysis of the meaning of the numbers for both 20w40 and 20w50 motor oils.

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What is 20w40?


Your 20w40 motor oil is specially formulated for various engine types and is often suitable for standard new engines. The “20w” in 20w40 represents the oil’s viscosity in cold temperatures. The W is a short form for winter.

Therefore, the 20 indicates that the oil has a low viscosity during winter. This aids in starting and lubrication in colder weather. This number is based on the SAE (Society of Automotive Engineers) classification.

The “40” part indicates that the oil has a moderate viscosity at high temperatures. It means that the oil provides adequate protection at higher temperatures without becoming too thin.

What is 20w50?


20W50 motor oil is typically used in older vehicle models. This is due to the fact that it protects and cushions the engine system against friction. As in 20w40, the “20W” part indicates how the oil flows at lower temperatures, particularly in colder weather.

Both 20w40 and 20w50 perform similarly in winter with a pour point of -30 degrees Celsius.

The “50” part indicates the oil’s viscosity at higher temperatures, such as when your engine is running hot. The higher number, like 50, indicates that the oil is thicker and has a higher viscosity. This helps maintain adequate lubrication and protection for the engine components.

To get the SAE class of both motor oils, they are passed through a viscometer at 100 degrees Celsius, which records the oil’s viscosity when it is hot. The 100 degrees Celsius mark represents the optimal working temperature of an engine.

Differences Between 20w40 And 20w50

The key differences and considerations between 20W-40 and 20W-50 oils are as follows:

Hot Temperature Performance

When it comes to hot temperature performance, the differences between 20W-40 and 20W-50 become more noticeable. 20W-50 oil is designed to perform better in high-temperature environments. This is made possible as it can handle temperatures of up to 267 degrees Celsius (flash point).

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It retains its viscosity and lubricating properties even as the engine heats up to extreme temperatures. This makes it an excellent choice for hot climates or engines subjected to high revs and temperature conditions.

While 20W-40 performs well in high temperatures, it thins out slightly more than 20W-50. This becomes a problem in extremely hot environments or engines that generate a lot of heat.

Fuel Efficiency

The viscosity of motor oil also has an impact on fuel efficiency. Thicker oils have lower fuel efficiency because they require more energy to circulate within the engine due to their higher viscosity.

Conversely, 20W-40 oil is slightly thinner, which means it flows more smoothly and provides a slight advantage in terms of fuel efficiency. Note that other factors also play a significant role in determining fuel efficiency. These factors include driving habits, vehicle maintenance, and the engine’s overall condition,


20W-40 oil is often considered a more versatile option because it falls in between the thinner oils like 10W-30 and the thicker oils like 20W-50. It is used in a wide range of engine types, including newer and older gasoline engines.

20W-50 oil is less versatile in comparison, as it is better suited for high-stress and high-temperature environments. This includes the hot climates and high-performance or older engines.

Price Difference

20W-40 is priced at $381 per liter, and 20W-50 is $445. The price difference demonstrates how the thicker 20W-50 oil is sometimes priced higher than the thinner 20W-40 oil.

Influence On RPM

Because 20W-50 oil is thicker at high temperatures, it reduces internal friction within the engine. Lower internal friction leads to smoother and more efficient engine operation. This allows the engine to rev more freely.

See also  20w40 vs 10w40: Which Viscosity is The Best for Your Engine in Winter?

On the other hand, 20W-40 oil has a slightly lower viscosity at high temperatures. This causes slightly more internal friction within the engine, resulting in more resistance, making it unable to handle higher RPMs.

Which One Is Right For You: 20W40 Or 20W50?

20W-50 oil is better suited for you if you are in an area with hot climates or you have either an old or a high-performance engine. It provides a thicker lubricating film at high temperatures, which can be beneficial for engines that run hot and require higher revving.

On the other hand, 20W-40 oil is a better choice for you if your vehicle has a standard engine. This is because its viscosity is suitable for normal driving conditions where you do not need high revs or engines that run hot. This, in turn, makes it more budget-friendly and more fuel-efficient.


Here are other related questions about 20w40 vs 20w50 motor oil you may want answers to.

Q1. Can 20w40 and 20w50 be used interchangeably?

You should not interchange them. Using the wrong oil can lead to engine wear and even potential damage. Stick to the recommended viscosity for your engine in your manual.

Q2. What does a multi-grade oil mean?

A multi-grade oil, also known as a multi-viscosity oil, refers to the oil having two distinct viscosities: one at low temperatures and another at high temperatures.


The choice between 20w40 vs. 20w50 motor oils is not merely a matter of numbers. It’s a decision that directly impacts the health and performance of your engine.

By understanding the significance of these numerical designations, you gain valuable insight into how these oils behave in both cold and hot conditions. 20w40 strikes a balance between being budget-friendly and fuel-efficient. This makes it a sensible choice if you own a vehicle with a standard engine. On the other hand, if your engine faces extreme temperatures, heavy usage, or you prioritize robust engine protection, 20w50 emerges as the preferred option. Always start by consulting your vehicle’s owner’s manual or contacting the manufacturer for their oil recommendations.

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