SAE 40 Vs 10W40 | Is SAE 40 Same As 10W40?

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Motor oil is an essential lubricant to run an engine smoothly. The two most common oil grades are SAE 10W 40 and SAE 40. But they are not the same; there is a difference between these two products. SAE stands for Society of Automotive Engineers, a professional organization that developed a numerical code system for grading motor oils based on viscosity.

Motor oil (engine oil) properties and specifications are one of the most critical factors when selecting a lubricant. Different oils are designed for various engines, and when choosing the right oil, you want to ensure that it matches your engine’s specifications. These lubricants thicken at cold temperatures and become thinner at high temperatures.

This article will discuss whether SAE 40 is the same as 10W40 motor oil. SAE 40 Vs 10W40 difference and showing which is best for your engine.

SAE 40 vs SAE 10W40 motor oil

What is SAE 40?

SAE 40 is a monograde lubricant made of mineral or synthetic-based oil. It is used in many vehicles, including cars, trucks, motorcycles and, generators, boats, and RVs. SAE 40 is a common engine lubricant oil that reduces the wear and tear of engine metal parts. It offers high performance. However, it has minimal additives.


What is SAE 10W40?

SAE 10W40 is dual-grade motor oil, and it has dual viscosity grades. At colder temperatures, its viscosity grade is 10W, and at a higher temperature has a viscosity grade of 40. The lubricant “W” letter means winter, and the numbers are the oil’s viscosity at high and low temperatures. 

This motor oil performs the same function as other oils but has some advantages over monograde oils. 10w40 can resist heat and cold better than other monograde oils, which can protect your engine from damage. The SAE 10W40 lubricants are made of synthetic, semi-synthetic, or conventional base oils, with different additives to enhance performance and reduce engine parts wearing.


Is SAE 40 the same as 10w40?

The simple answer is No. The SAE 40 and SAE 10W40 is different motor oil. The main difference between these two lubricants is cold temperature viscosity. SAE 40 mono-grade oil has a lower viscosity index and higher pouring point temperature than the SAE 10W40 motor oil.

This means multi-grade SAE 10W40 performs better in hot and cold temperatures than the monograde SAE 40. It slowly thins at high temperatures and quickly flows at lower temperatures, providing better protection against the wearing of the engine’s metal parts.

These two motor oils come in various base oil blends like conventional oil, full synthetic, synthetic blend, and high mileage oil. However, the significant difference between SAE 40 vs 10w40 oil is viscosity rating at high and low temperatures and pouring point temperature.


The main difference is SAE 40 vs 10w40.

The significant difference between SAE 40 vs 10W40 is viscosity and pouring point temperatures.

When the engine starts, its metal parts are subject to friction, thus generating heat and increasing metal parts wearing. The motor oils lubricate the engine’s inner parts, make a thin layer between pistons and cylinders, reduce friction, and cool the engine parts.

These viscosity and pouring point temperatures are essential for protecting against wearing the engine’s metal parts. Thicker oils protect against wearing metal parts at higher temperatures than thinner oils; However, thicker lubricants flow slowly at low temperatures. This causes the metal parts to wear at a cold start.

Viscosity: The viscosity means motor oil is resistant to flow. Thicker oil has a high viscosity, and they are thinning when the temperature rises. Which means it becomes thinner gradually at high temperatures. Thicker lubricant is essential to reduce the engine parts from wearing, and if the oil thins quickly when the temperature increases, the engine parts rapidly wear.

Pouring point: The pouring point means the lowest temperature at that fluid flows. If the oil has a higher pouring point, it flows slowly at a low temperature. High pouring point motor oil increases the wearing at cold startup.

Due to the multi-grade 10W40’s oil flow easily at low temperatures reduces engine wear at cold startup, and Furthermore, it thinning slowly at high operating temperatures. Therefore, multi-grade oils perform better lubrication in cold and hot operating temperatures.

The following motor oil specification table shows that the same manufacturer’s SAE 40 product has a lower viscosity index and a viscosity grade at 100°C than the SAE 10W40 multi-grade lubricant. Therefore in the performance stand, SAE 10W40 is the clear winner.

PropertyMobil HD 40Valvoline Daily ProtectionValvoline High MileageValvoline Daily Protection
GradeSAE 40SAE 4010W-4010W-40
Viscosity IndexN/A103154150
Flash Point, °C247N/AN/AN/A
Kinematic Viscosity @ 100 C, mm2/s15.513.515.715.5
Pour Point, °C-21-15-33-33


Can I use 10w-40 oil instead of SAE 40 oil?

Yes, you can use 10W-40 motor oil instead of SAE 40. Multigrade 10W-40 is more advanced and has a better viscosity rating. Hence, there is no performance degradation. Even at a lower temperature, multi-grade oil flows well in the engine. However, before using a different type of oil, always check the manufacturer’s recommended API index.


Engine oil refilling


What is SAE 40 equivalent to?

The close equivalent to SAE 40 motor oil is SAE 0W40, 5W40, 10W40, 20W40, etc. You can use any multi-grade motor oil that has 40 after the W sign. However, most modern engine manufacturers recommend multi-grade motor oils for better performance in cold and hot temperatures.



Can I use 10w-40 oil instead of SAE 30 oil?

You can use SAE 10W-40 motor oil instead of SAE 30, but it is not the perfect match. This is because SAE 30 has a lower viscosity index than the 10W-40. Therefore SAE 30 flows more quickly than SAE 10W-40. Therefore it can slightly increase the engine parts wearing. The SAE 30 equivalent multigrade oil is 0W30, 5W30, 10W30.



What is the difference between 10w-30 and 10w-40 motor oil? (10W30 vs 10W40)

The main difference between 10w-30 and 10w-40 motor oil is high-temperature viscosity. Viscosity means how fast oil is thin at high temperatures. At low temperatures, these two motor oils have the same viscosity index. But the 10W30 motor oil has a lower viscosity index, which means it is thinner faster than 10W40 oil.

The 10W30 oil is suitable for colder climates (-30°C/-22°F in the winter and 35°C/95°F in summer), while 10W40 is suitable for warmer temperatures. You can use these two products depending on your region’s ambient temperatures. But make sure you choose the correct API rating specified by your car manufacturer.


The final word of SAE 40 Vs 10W40.

SAE 40 and 10W40 are the Society of Automotive Engineers’ motor oil ratings. The SAE 40 is single-grade motor oil, and SAE 10W40 is multi-grade. Multi-grade oils perform better in cold and hot temperatures, while single-grade oils perform better only in hot temperatures.

The main difference between these two motor oils is the viscosity at lower and high temperatures. SAE40 is not suitable for low ambient temperatures, and SAE 10W40 is ideal for low and high ambient temperatures. SAE40 is thick at a lower temperature and slowly flows at a cold engine start; therefore, it can increase engine wearing. However, SAE 10W40 flows quickly in a cold startup, gradually thinning at high operating temperatures.


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