75w90 vs 80w90: A Detailed Comparison of Two Gear Oils

75w90 vs 80w90 gear oils both help to protect car hardware components from rust, corrosion, and oxidation.

75W90 Vs 80W90

These oils share some similarities, but they are completely different, and it’s important to know these differences before choosing one for your car.

We’ll compare both gear oils in this article so you can know their various applications and choose the best one according to your needs.

Features 75w90 80w90
Density 0.86 0.90
Oil type Fully synthetic or semi-synthetic Multi-grade manual transmission
Applications Limited slip differentials, manual transmissions, and heavy-duty truck axles 4WD, agricultural and construction equipment, trucks, and light commercials.
SAE Grade   75w90 80w90

What Are the Main Differences Between 75w90 and 80w90?

The main differences between 75w90 and 80w90 are their viscosity and density. 75w90 gear oils have a higher viscosity index than 80w90, while the 80w90 oil is denser than 75w90 oil. This makes the 75w90 oil ideal for higher temperature conditions to reduce the degradation of the oil.

There are other factors that differentiate the two gear oils, and we’ll go through these factors in detail so you can understand these differences.

– Density

Density and thickness are interrelated, and the higher the density of gear oil, the thicker it will be. 75w90 gear oil has a density of 0.86, which is lower, but sufficient to provide protection against wear and tear. The oil is thin and suitable for use in extreme conditions, with reduced maintenance costs.

On the other hand, 80w90 has a density of 0.90, which gives it enough thickness to withstand high temperatures and offers protection against wear and tear. However, a common thing with gear oil that has high density is that they easily become clumpy and degrade at low temperatures. The higher density rating of 80w90 gear oil makes it a better option than 75w90 gear oil.

– Viscosity

Another notable difference between the two engine oils is their viscosity, which also influences thickness. Gear oils are designed with sufficient thickness to allow them to prevent moving components from wearing out during operation. As mentioned earlier, 80w90 oil is thicker than 75w90, meaning that it will provide a higher level of protection for your gears.

Thicker oils and lubricates are defensive, which is why 80w90 oils are mostly used for high-performance applications. 80w90 gear oils are made from mineral oils and often require regular oil adjustments and maintenance. The oil thickens at a lower temperature, which can cause degradation and lower the efficiency of the oil.

On the other hand, 75w90 offers constant viscosity at different temperature conditions. It is generally more stable than 80w90 in both cold and hot conditions.

– Thermal Stability

Thermal stability or operating temperature is another factor to look at when comparing the two gear oils. 75w90 is thermally strong, shear stable, para-synthetic, and thermally stable. The lubricant oil is multi-grade, making it an ideal option for all drive applications. It’s important for gear oil to be able to work under different temperature conditions, and the 75w90 gear oil can withstand temperature range between 300 to 350 degrees Fahrenheit.

On the other hand, 80w90 gear oil offers impressive versatility in both high and cold environments. The oil can perform optimally under temperature conditions between -20 degrees Fahrenheit and 400 degrees Fahrenheit. With that being said, the oil can perform effectively in winter and in summer.

In addition to thermal stability, protection is another important difference between 75w90 and 80w90. The 80w90 gear oil is the winner in this case, as it offers more protection against wear. However, this oil can cause your engine to move harder when subjected to some types of applications. On the other hand, 75w90 can be used for a wider range of applications, even though it doesn’t provide as much safety.

– Additives

The two gear oils are similar in terms of composition and efficiency. 75w90 oil is designed with adhesive packaging that creates a coat around gears to prevent them from wearing. The oil is amazingly reliable, sleek, and non-foaming, making it a perfect option for heavy-duty applications.

On the other hand, 80w90 oil features anti-wear and lubricating agents to prevent gear tears. The oil is also equipped with additives that can control varying heat conditions, which is why they are recommended for use during different seasons.

– Application

The differences in their viscosity and density make their application also different. As mentioned earlier, 80w90 can be used in summer and winter because of its ability to withstand extreme weather conditions. 80w90 oil can be used in agricultural equipment, transfer cases, manual gearboxes, light commercials, 4WDs, and trucks.

75w90 oil can also be used under different temperature conditions, but mostly on the higher end. The oil is designed to withstand the stress from high temperatures, and it’s the preferred option for heavy-duty axles, final drives, and transmission.

– Price

Another area where the two gear oils differ is in their prices. When buying gear oil for your vehicle, it’s important to ensure that the oil can reduce maintenance costs and offer value for money.

The ability of 75w90 to operate under different temperature conditions and its dynamic nature makes it more expensive than 80w90 gear oil. However, you can be sure that it’s a worthy investment.

– Overall

Despite the differences between the two gear oils, they also share some similarities. For example, they are both SAE viscosity-grade gear oils. Also, they are both winter stable oil, as indicated by the W in their name. They are both multi-grade viscosity gear oils that can be used under all weather conditions.

Their fire point, pour point, and flash points are also similar, and the two oils offer protection against corrosion, rust, and wear. In addition, you can use both the 75w90 and 80w90 oil for similar applications but bear in mind that the 80w90 is a more flexible option in terms of its applications.

– Heaviness

75w90 gear oil is not heavier than 80w90. In fact, the 80w90 gear oil is the heaviest on the market today, which is why it’s used for heavy-duty applications. The oil can also be used for a lighter application, which is not always necessary.

The ideal option to use for these light applications is the 75w90 gear oil since it can provide the type of protection needed.

– Mixing

Mixing 75w90 gear oil with 80w90 depends on many factors, which include the type of vehicle you have and what you want to achieve from the mixture. If you’re only topping the level of oil without draining the old one, the mixture won’t cause any harm. This is because the viscosity of the mixture will be between both grades, and your vehicle engine will stay lubricated.

However, the best thing to do is to maintain a single consistency, especially when you’re completely changing the oil. With that being said, you can always determine the exact oil viscosity in your engine. Also, you can use 80w90 in place of 75w90, but this should only be done with proper consideration of different conditions.

For clarity, you can check your car’s owner’s manual for the specific viscosity grade and oil type to use. Alternatively, you can also ask a trusted mechanic for their opinion.

What Are the 75w90 Characteristics and Specifications?

The 75w90 characteristics and specifications are that the oil is a fully synthetic gear oil with a versatile range of applications. This gear oil also has a range of additives that make it function excellently in extreme temperatures and pressure conditions.

Specialties of 75w90 Gear Oil

75w90 gear oil is made from a synthetic oil base, together with some unique lubricants that allow it to function under extreme temperature and pressure conditions. It is the ideal type of oil to use in limited-slip differentials and colder climates. The oil is generally known for its versatility, especially in terms of application.

– Specifications

75w90 describes the SAE class of the oil, with the W indicating that the oil is winter suitable and can maintain its flowability at cold temperatures. Gear oils that have 75W are able to able to maintain their flowability at -40 degrees Fahrenheit. The value 90 in the name stands for the kinematic viscosity of the oil at 212 degrees Fahrenheit (100 degrees Celsius).

Another key thing to note about the 75w90 oil is that its viscosity index is 144. The oil is designed to be tough and steady, making it suitable for any type of driving need. It is also resistant to the impact of oxidation, a vital quality that every lubricant should possess.

The kinematic viscosity of the oil at 104 degrees Fahrenheit is 115, and the flash point of the oil is 410 degrees Fahrenheit.

– Benefits of Using 75w90 Gear Oil

The main benefits of using 75w90 gear oil include the following:

  • The gear oil offers a longer life span compared to options on the market.
  • It is designed to be resistant to foaming.
  • 75w90 oil offers an impressive film strength to guarantee reliable lubrication.

Basically, 75w90 gear oil is the best option for anyone looking for a gear oil that can serve different purposes.

– The Best 75w90 Gear Oil Brand

The best 75w90 gear oil brand is not easy to determine, as there are many brands on the market with different and unique features. However, some of the popular brands of 75w90 that you can count on include Mobil, Royal Purple, Castrol, and Valvoline. Interestingly, these brands also offer 80w90 gear oil.

Regardless of the brand you choose, the most important thing is to ensure that it is ideal for your car. You can check your car’s owner’s manual for specific gear oil recommendations and requirements.

What Are the 80w90 Characteristics and Specifications?

The 80w90 characteristics and specifications include its ability to withstand high temperatures and heavy loads. This makes the oil an ideal option for race cars and other high-performance vehicles. You can also use 80w90 oil in trucks and SUVs, particularly for off-road driving.

Specifications and Features of 80w90 Gear Oil

Applications that require extreme pressure, as well as the lubrication of non-synchronized manual transmission, can enjoy the benefits of 80w90 gear oil. Conventional clutches and limited-slip differentials can also use this type of oil.

– Specifications

Like 75w90, 80w90 represents the SAE class of the oil, with W indicating that the oil can function properly and maintain its stability in the winter seasons. It’s important to note that 80w90 oil has two viscosity grades. The value 80 represents the workability index of the oil, and it shows that the oil offers an impressive performance in subfreezing conditions.

The value 90 also represents the thickness and kinematic viscosity of the oil at 212 degrees Fahrenheit (100 degrees Celsius). 80w90 oil can flow at 79 degrees Fahrenheit, unlike other options on the market.

The viscosity index of 80w90 oil is 90, and the flash point of the oil is 432 degrees Fahrenheit. 80w90 oil is also versatile and suitable for use in low and high-temperature conditions.

– Benefits of Using 80w90 Gear Oil

The benefits of using 80w90 gear oil include the following:

  • It is one of the most thermally stable oils on the market.
  • The load-carrying capacity of the oil is impressively high.
  • 80w90 gear oil offers amazing protection against corrosion, rust, and other effects of oxidation.

The 80w90 gear oil is the option to look at if you want an oil that is better suited for high-performance applications.


75w90 vs 80w90 are synthetic oils with similar additives and components. However, the way you use both oils depends on their capabilities. We have highlighted the main differences between the two oils to guide you through choosing which one is more suitable for your needs. Consider choosing 80w90 gear oil if you are after high-performance applications and more protection, but 75w90 offers more versatility.

However, always have it in mind that your engine will work harder on 80w90 than on 75w90. In terms of stability, especially under extreme weather conditions, the best option to choose is 75w90, and this is because it’s a thinner gear oil. The oil is designed to maintain viscosity while providing protection under different temperature conditions.

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