75w85 vs. 75w90 Gear oil: Which Is Better And Why?

Getting more consistent with gear oil usage. But, before buying the right gear oil, you should consider some controls. And regarding gear oil, 75w85 and 75w90 are the top choices among car owners.
Modern-day cars demand modern-day engines; with every change, it needs the most updated oil, featuring the latest and highest quality.
If there is any difference between 75w85 and 75w90, it is too far to compare. 75w90 is an overall better oil, while 75w85 is “considered” to provide better fuel economy.
However, 75w85 vs. 75w90 are two popular options that users often use. So what is the difference between them, and which oil is the best? Find out in the article below.

 75w85 vs. 75w90 gear oil

What is 75w85 Gear Oil?

75w85 is a synthetic gear oil and is best for many vehicles, including trucks and cars. 75w85 oils are also known as API CK-4. And 75w85 gear oil gl5 is also used for generators, marine engines, and other high-power machines.
Also, it’s a popular oil because it lasts longer than traditional oil. Besides, 75w85 gear oil has a higher API gravity rating than conventional oils. So it can give better protection over time.
Moreover, this 75w85 base oil decreases friction and wear in internal burning engines. Additionally, it contains a light viscosity index, allowing it to flow easily through the system. This characteristic makes it perfect for vehicles that drive long distances, like trucks or SUVs, daily.

Example of Redline's 75w85 full synthetic gear oil

What is 75w90 Gear Oil?

75w90 is a medium-viscosity grade synthetic base oil used primarily in diesel engines. In addition, it contains a higher viscosity grade of 90. Hence, it’s formulated to deliver optimum performance for your car with improved fuel efficiency compared to previous formulations.
Most importantly, this oil comes with anti-wear additives to prevent metal wear during long-term operation. Gear oil 75w90 is considered an “extreme” grade oil. It’s because it contains a high viscosity index and can tolerate very high temperatures.
A more important reason to choose this oil is that it is formulated with a unique additive package. This additive formula allows your engine to stay cleaner on your engine than other oils.

a 75w90 gear oil example produced by Mobil 1

What Is The Difference Between 75w85 And 75w90 Gear Oil?

There are definite differences between 75w85 and 75w90 gear oils. If you choose a suitable product, these are the main points you need to pay attention to. So, here is the comparison of 75w gear oil vs. 75w90. Let’s start with the following:

Kinematic Viscosity

Kinematic viscosity is important to grade gear oil for winter use. In winter, the gears get stuck, which can be a significant problem and stop the engine from working.
So, when lubricant is applied, it reduces the friction, which prevents the gears from working, thus providing the gears with a little more flexibility.
You know that the higher the grading, the higher the viscosity. So, you can grade the viscosity of 75w85 as 85, which is a medium layer thick, which means more consistency.
75w90 is thicker than 75w85. Particularly, it’s a winter-grade lubricant oil. For winter-grade lubricants, oil thickness is required. So, with extended thickness, viscosity also enhances.

See Also: Thickest oil


Additives come after viscosity grading or marking. We all know that viscosity is the most important factor in lubricant oil. But apart from viscosity, there are other factors for a lubricant, and one of them is additives.
75w85 contains anti-rust additives. Actually, this provides a special ability to prevent rust from forming on the gears. And also, the used additives in 75w85 are quite good at handling the pressure.
Good additives mean good traction. If the lubricant additives are of good grade, you can start your engines faster in the winter season. In this case, 75w90 is the best because its viscosity changes proportionally with temperature because of additives.

Shear Resistance

Shear resistance can change your lubricant thickness. According to this thickness, you can select oil for your engine, which can extend the traction of your engine.
75w85 has a medium thickness. Ergo, the shear strength of 75w85 is comparatively smaller. But by adding external reinforcement, an improved shear stability can be found.
75w90 has good shear stability. 75w90 is much thicker than 75w85. Because of the additives. This oil’s shear resistance is also good.

Pros and Cons of 75w85 Vs. 75W90 Gear oils:

Pros Of 75w85 Gear Oil:

● Better performance
● Better fuel economy
● A unique amount of friction
● Compatible with high-performance engines

Cons Of 75w85 Gear Oils

● Average life and replacement time
● More engine wear

Pros Of 75w90 Gear Oil:

● Great oxidation stability
● Less engine wear
● Excellent life
● Better replacement time

Cons Of 75w90 Gear Oil:

● Poor oxidation stability

75w85 vs 75w90 Tacoma

Which is Better: 75w85 Vs. 75w90 Gear Oil?

75w90 is a better choice. The reason is that these gear oils provide great oxidation resistance compared to 75w85. Furthermore, it contains little engine wear and can last longer than other common gear oils.
Best of all, it has a great replacement interval of around 70,000 miles, making it the best gear oil ensuring optimal performance for the foreseeable time to come.

75w85 vs 75w90 Tacoma:

It’s best to use 75w85 gl5 type gear oil in the differential in a Tacoma truck. You can also use Toyota brand gear oil or redline lightweight 75w85s. On the other hand, you can use 75w90 gear oil in your Tacoma, and it would be the best option.

FAQ (Frequently Asked Questions):

Q. Can I mix 75w90 with 75w85?

You can’t. But as the viscosity of both oils is near 85/90, you can mix 75w90 with 75w85. It’s because if you mix 75w90 with 75w85, they won’t damage your car. But after mixing them, if you notice the oils becoming dirty, and damaging your car, remove them. And pour the best oil into your engine.

Read Also : Can you mix 5W20 and 5W30

Q. What is 75w85 gear oil used for?

Basically, 75w85 gear oil comes from high-quality base oils and an advanced additive system. Mainly, this product is used for automotive transmissions, final drives, and axles.

Q. Is Toyota 75w85 gear oil Synthetic?

Toyota 75W-85 gear oil is a full synthetic and OEM standard fill fluid used in non-limited slip applications.

Q. Can I use 75w85 instead of 75W90?

Yes, you can use 75w85 instead of 75W90. The two oils are very similar, and one will work better in your car. The main difference between the two is the oil viscosity or thickness.
Usually, 75W90 is slightly thicker than 75w85, so it can offer better protection for your engine in extreme conditions. However, both oil can do a good job to keep your engine running smoothly and cleanly.

Final Word

Finally, we hope you found a nice 75w85 vs. 75w90 gear oil comparison. Both oils are quite effective. And also, they can work together. These lubricants are suitable for winter because they don’t clog your gears when used in colder temperatures.
Among both lubricants, 75w90 is slightly more efficient. But the change is similar. Hopefully, from this 75w85 vs. 75w90 ram, you can choose the best one for you. Best of luck.



I am Engr. Z Eusuf Lubricant Specialist, Mechanical Engineer & has been working with engine lubricants for a long time and knows what makes them work best. I can help you find the right oil for your needs, and I have tips on how to keep your engine running at its best.