75w90 vs 80w90 gear oil

Gear oil and lubricants play a vital role in a car’s components. They protect the car hardware from oxidation, corrosion, and rust. Without oils and greases, there will be more harm to the components, especially in the gear system.

However, not all oils are ideal for a particular car gear as oils differ in viscosity and other factors. Viscous oil gives better protection than thin because of its thickness consistency.

Transmission units operate at high speeds, pressures, and temperatures, which is why transmission oil is necessary for the efficient functioning of the structure.

It is crucial that the transmission oil has the proper viscosity characteristics in order to provide proper starting characteristics and long-term performance. How viscous should the oil be?

Moreover, this viscosity can affect the efficiency of your car’s gears due to considerable thickening at cooler or moderate temperatures.

With this, it is clear that having high-quality oil can provide your car gear with the protection and efficiency required. So, between 75w90 and 80w90 gear oil, which one could be ideal for your car? Stay tuned.

But before we dive in with the properties, you should remember that gear oil with a viscosity of 75w90 or 80w90 should, first and foremost, be chosen according to the manufacturer’s recommendations.

Since they know how the transmission works, they can tell you with certainty which fluid will work best for your vehicle. Moreover, this is very useful, since it is unlikely that the manufacturer of lubricating fluids will miss the opportunity to include tolerances from engineering companies on the bottle label (as most do).

75w90 gear oil

Transmission oil 75W-90 is used in extreme-pressure applications and is recommended for limited-slip differentials and for use in cold climates.

Used in heavy-duty manual transmissions, final drives, and axles, high temperatures do not affect the heavy film left by this oil.

This is a high-performance one hundred percent and multi-purpose gear oil with an anti-friction treatment. The 75w90 stands for SAE class. The W stands for the oil’s flowability in cold temperature conditions.

The W means that the oil is still flowable to up to -40 degrees celsius or -40°F. The “90” on this oil is the oil’s kinetic viscosity at one hundred degrees celsius.

Viscosity index

75W 90 gear oil’s viscosity index is 144.

Temperature range

The oil has robust and stable properties ideal for the vehicle’s all drive operations. It is resistant to thermal effects and oxidation This oil is best for use in freezing temperatures and pressure conditions.

The temperature range for 75W90 gear oil is between 300 degrees Fahrenheit to 350 degrees Fahrenheit or 148.8°C to 176.6°C.

Kinematic viscosity

The oil’s kinematic viscosity at 40c is 115.


This oil’s flashpoint is at 210 degrees Celsius or 410°F.

80w90 gear oil

80W-90 gear oil can be used in extreme-pressure applications and as a lubricant for non-synchronized manual transmissions in heavy trucks or buses. This gear oil is recommended for conventional and limited-slip differentials.

The 80 W 90 numbers refer to the oil’s viscosity grades. This gear oil has two viscosity grades and two numbers. The W in this oil stands for oil’s stability in winter.

The number 80 on this oil implies that this oil has excellent workability at cold temperatures. The second number, “90,” denotes the oil’s thickness at one hundred degrees Celsius.

The oil can be flowable in temperatures of even -26 degrees Celsius or -14.8°F. The number 90 is the oil’s kinematic viscosity at one hundred degrees celsius.

Therefore its kinematic viscosity can range between 13.5 to 18.4 square millimeters per second. The oil can withstand heavy loads and features high shear stability.

Viscosity index

The oil’s viscosity index is 90.


The flashpoint for 80W 90 gear oil is 222 degrees celsius or 431.6°F.

Temperature range

This is a versatile oil ideal for both high and low-temperature conditions; both summer and winter. The temperature range for this oil is -25 to 35 degrees celsius or -13°F to 95°F.

Differences between 75w90 vs. 80w90 gear oils

  • 80W 90 gear oil is denser than the 75 W 90 gear oil.
  • Due to its thinness, 75w 90 gear oil offers better gear protection than its thicker counterpart. Therefore deemed to be good overall.
  • 75W90 gear oil has a consistent viscosity and thickness across a wide range of temperatures.

Advantages of 75w90

  • Excellent resistance to foaming
  • Grants longer seal life
  • Has a good film strength maintenance which enhances reliable lubrication

Pros 80w90 gear oil

  • Has high thermal stability
  • Offer excellent protection against rust and corrosion
  • Has a high load-carrying capability

Similarities between them

  • Both oils have almost similar flashpoint, pour point, and fire point temperatures.
  • Both are safe for use with open differentials, manual transmissions, and limited-slip differential in heavy-duty trucks.
  • They both can protect against wear, rust, and corrosion.
  • Both are ideal for heavy city use and can handle extreme pressure.

Can I mix 75w90 instead of 80w90?

Yes, you can mix these oils and use the mix, but it is always advisable to consult your car manufacturer’s manual. It is also essential to consult your mechanic before you mix.


The 75W90 and 80w90 are synthetic oils featuring the modern additive system. These oils have different applications based on their capabilities.

The 75W90 gear oil is best for use in extreme temperature conditions. It is recommended for use in cold temperatures and limited-slip differentials.

The 80W90 oil, on the other hand, is the best oil for non-synchronized manual transmission in heavy-duty cars and trucks. It is best for limited slip and conventional differentials.

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