75w90 vs 80w90: How to Choose the Perfect Gear Oil?

Paulo Santos Goncalves

Are you stranded on what to go for between 75w90 and 80w90 Gear Oil? Our review article has sorted out everything you need to know. While they seem the same, oil and gear oil are different. Keep reading our article for more.

Besides lubricants, gear oil plays a vital role in your car; on top of the rust protection, it also helps you manage oxidation and corrosion, giving your car a smooth environment to run well. Thus, gear oils are online, and they come in different weights. Due to these minor differences, many people have a hard time deciding which is better than the other.

First, the application differs, and the viscosity is the primary aspect that makes them unique. This brings us to today's topic: the 75w90 vs 80w90 gear oil. We will guide you through the article to ensure you get the perfect gear oil that meets your needs. You understand that the transmission unit needs high speed, pressure, and high temperature to work, which calls for efficient transmission oil.

To this far, you might ask yourself if you can utilize 75w90 & 80w90 interchangeably. Keep reading our article to the end and make the right decision. Understanding the functionality, differences, and similarity will give you a clue on what gear oil to go for and for what target.

Table Of Contents

Differential Oil and Gear Oil

These two terms sound the same, but they are somewhat different. First, you must understand that gear oil is meant to lubricate the transmission in a car, while the oil, specifically the differential oil, is meant to lubricate the differential car.

While sometimes you can use these two interchangeably, we do not recommend it for a reason. This is because differential oil tends to be thinner, which means it does not guarantee enough protection like gear oil. Still, when you use unauthorized gear oil in your transmission and differential, you must expect damage to the seals and gaskets.

Thus, using the oil meant for a particular task is highly recommended. We are here to help you understand the difference and similarities between the 75w90 and 80w90 Gear oil. Let us start with the overview below.

75w90 vs 80w90 Gear oil review

To an extent, you might get confused and conclude that 75w90 & 80w90 are the same. The synthetic gear oil 75w90 and 80w90 has slight differences; these SAE numbers indicate different grades. To be more specific, gear oil has a number from 60 and above, which implies explicitly that both the above are gear oil. Let us now dive into the specifications of each gear oil.

75w90 Gear oil

75W90  is one of the most versatile gear oils on the market and has many applications. This is because the oil can handle the moderate temperature and load. Thus, it is efficient when used on light vehicles such as passenger vehicles and light trucks. Hence the oil is multi-purpose and has indicated a high performance when used as an anti-friction treatment.

Still, 75W90 can handle robust automobiles, including the SUBs, and this excludes high-performance application cases. Mainly, it's utilized in multiple railway gearboxes. This is due to its incredible load spot function, precisely when intense pressure and load are needed.

In other words, 75W90  has an excessive viscosity index, thermal stability, extremely low-temperature fluidity, low pour point, and high oxidation. The unique feature of this gear oil lies in the impressive foaming power, which guarantees a long seal lifetime, while the perfect film strength maintenance enhances reliable lubrication.

80w90 Gear oil

This is a high-performing synthetic gear oil.it is designed to target heavy vehicles, which often experience wear and tear. Thus, you can use 80w90 as a lubricant among the non-synchronized manual transmission on trucks or buses. Another targeted area is the place with extreme pressure. Thus, we recommend this gear oil in place with the conventional differential as well as limited slip.

This is because the gear oil features two viscosity grades. 80w90 withstands heavy loads and extreme temperatures, making it effective even on race cars, high-performing trucks, and buses. You can also utilize it on SUVs with frequent off-road driving. W in this access indicates the stability of the oil during winter, and 80 is a clear indication that oil is ideal even in freezing temperatures.

At the same time, 90 is the gear oil viscosity recorded at the thickness of 100 degrees Celsius. On the kinematic viscosity range, we will dive into it later on in this article. Otherwise, the oil has a high shear stability feature making it effective on the heavy load.

However, the oil works well at low temperatures; hence it is also a multi-purpose gear oil applicable from the axle of the spiral to the gears in the manual transmission. It features strong resistance on the foam, which is ideal for curbing corrosion, and comes with excellent flexibility. If you want your vehicle to get the best performance, then get 80w90 gear oil with a compatible partner.

Differences Between 75w90 and 80w90 Gear Oil

Because all exist in liquid form, it becomes challenging to differentiate gear oil. However, there are some aspects you can count on to notice the differences. Among them are the grade and SAI number classification. Besides material, you can use several factors to differentiate the 75w90 and 80w90 gear oil. Let us dive into these factors and find out the differences:-

1. Viscosity

The fact remains that 80w90 is thicker when you compare it with 75w90. Thus, 80w90 guarantees extra protection and is utilized among high-performing machines or applications. Still, 75w90 has numerous applications in our daily life. In summary, thick lubrication is defensive; thus, gear oil can help maintain the sensitive axle even in challenging surroundings.

SAE 80w90 is sourced from mineral oil and needs frequent maintenance; note that low condensation temperatures often interfere with production. While 75w90 features a good temperature range and constant viscosity. Remember that the gear oil's thickness is what we call viscosity. At lower temperatures, 80w90 is denser than 75w90. This means 75w90 is more effective not only during hot conditions but also in cold weather.

2. Operating Temperature

Looking at the two gear oils, 75w90 is Germany strong, stable shear, para synthetic, and even thermally stable. Hence, it is ranked as multi-grade gear oil with many applications for most vehicles. The oils can stand the extreme ambient temperature between 300F to 350F. Somewhere else, 80w90 synthetic is effective in extreme environments and hence versatile.

Thus 80w90 is efficient for the temperature between -20F and 400F. We highly recommend this gear oil for your vehicle during winter and summer conditions, and it is because of this that 80w90 has a higher rating. On top, the gear oil tolerates stress and heat, which is ideal for a high-performing surface. However, remember that 80w90 might overstress your vehicle engine; utilize it carefully.

3. Density

There is a relationship between the density and viscosity of the gear oil. This implies that when the gear oil is denser, it translates that it is thicker. From the information, 80w90 synthetic gear oil features a density of 0.9, and when it comes to 75w90, you will find a density of 0.86.

Here, the thicker the gear oil, the more advantage you will enjoy regarding protection. But always remember that thick gear oil offers clumpy challenges during the low temperature, which is likely to downgrade the efficiency of your machine. In comparison, 75w90 is thick but provides much-needed protection in extreme weather situations while guaranteeing efficiency.

4. Pricing

We also must say something about the pricing of 80w90 and a75w90 gear oil while differentiating the two. Everyone online wishes to get a service that cuts the budget while keeping maintenance in mind. We must agree that 75w90 indicates constant viscosity as well as s thickness at an extensive temperature range.

However, it becomes thicker when the temperature becomes low, while at higher temperatures, it becomes thicker. Because of such a mechanism, 75w90 is more expensive than 80w90. Though pricier, the gear oil is balanced and worth paying such extra costs.

5. Uses And Protection

As we have noted, there is a slight difference between the two in terms of their viscosity and density, which results in different behavior at the extreme temperature. Such a feature has highlighted the usage variation. Thus most people prefer to use 80w90 during the winter and summer as it can withstand extreme temperatures hot and high. Thus utilize this oil on the manual gearbox, 4WDs, light commercial vehicles, agriculture, etc.

The 75w90 has a vast application area though preferred for the higher temperature range. It targets to help you manage premature wear or tear when your system gets in high temperatures. Thus, we recommend using this gear oil on heavy-duty manual transmitters, final drives, or axles.

Protection is another aspect. While 80w90 is ideal for making the engine run harder, 75w90 remains versatile with extensive applications. However, the 75w90 does not guarantee much protection against wear and tear compared to the 80w90.

6. Additives

When it comes to efficiency or composition, both the two gear oil give almost the same functionality. However, 75w90 contains a specific adhesive package responsible for coating your gear to prevent wear. Thus, due to its no-formation nature, it is extremely;y reliable, sleek, and ideal for heavy-duty. Expect high efficiency.

While 80w90 is only strengthened using the anti-wear and lubricating agents, which manage the wear or tear. It also contains the heat additive element rarely available in other gear oil. This makes the 80w90 gear oil perfect for racing cars and sufficiently performs well on heavy-duty applications.

Perfect Option 75W90 vs 80W90 Gear Oil

The two gear oils are SAE-grade oil on the market. As a customer, we also mention that you can divide the transition to the single stage as well as to the multistage viscosity to use on all weather temperatures. Still, you can categorize the single stage into low and high temperatures. For this case, 80w90 and 75w90 are multi-grade, thus ideal for all weather conditions.

The only difference is spotted when it comes to the low-temperature viscosity. W denotes the low temperature and efficiency in the winter. In front of W denotes low temperature while the smaller number is the higher density simplifying perfect low-temperature efficiency. However, the number found behind W indicates high-temperature thickness or viscosity.

The bigger this number is, the thicker the gear oil and the more influential the gear oil is on the high temperature. To simplify it, 80w90 and 75w90 have the same high-temperature efficiency, but 75w90 has more fluidity, robust low-temperature efficiency, and low-temperature thickness or viscosity. This means 75w90 is ideal and the best gear oil and is highly recommended even in the lower winder condition. The temperature application ranges from 45 degrees but not below negative 35 degrees.


Q. What is 75w90 or 80w90?

These two are the gear oil on the market. 75w90 is thinner while 80w90is thicker. W denoting the winter where 90 in both cases stands for the thickness is love call it viscosity. Each gear oil has a specific use case or application area due to their natures, as we have covered in the above article.

Q. Can I use 75w90 and 80w90 interchangeably?

Well, instead of 75w990, one can use 80w90. But one thing you need to note here is that the condition on which you are utilizing matters. Because 80w90 shows high viscosity hence suitable in extreme weather conditions.

Q. Can one mix 75w90 with 80w90 gear oil?

Because of the limited differences, customers can mix the two gear oils. Also, the mix will never, in any case, downgrade the performance of your car. However, we recommend you seek clarification from the car manufacturer before mixing the gear oil. Generally, users can mix the PAOgear oil but not the PAG-polyglycerol synthetic oil. Incompatible oil reacts to produce the gum gel.

Q. Does 80w920 have any benefits over 75w90 gear oil?

80w90 is indeed thicker; it gives your machine more protection, especially on the gears. But still, remember that this thick gear oil results in the car doing extra hard work. We highly recommend 80w90 for high-performance applications but typically, use 75w90 in your normal condition.

Q. Can one use the gear oil instead of the engine oil?

These two are different oils. Engine oil offers lubrication on moving parts in your engine, but gear oil only lubricates the transmission or differential. Though in some cases, one can utilize the engine oil rather than gear oil, we do not recommend that since engine oil doesn't offer the needed protection. Still, engine oil brings effects on the gaskets as well as seals.

Q. Is it a must that one should change the gear oil?

Sure, it is a must since the gear oil will break down and stop working as a lubricant in your transmitter or differential when you assume. Hence, expect wear and tear on the bearings, if not the gears. Change the gear oil based on the guidelines from the manual.


Gear oil is a vital car fluid you need to have. Among the grades, we have 75w90 and 80w90, though with many similar features; the two also indicate slight differences based on the condition. 75w90 has a broader application compared to the 80w90. In the above article, we have covered the two gear oils in detail and highlighted their differences for a better understanding. Each is ideal in different weather conditions. However, 75w90 is more stable, slightly expensive, and guarantees adequate protection and high performance. For extreme weather conditions, 80w90 is perfect, but many people prefer 75w90 because of the characteristics it exhibits and its low maintenance cost.

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