75w90 vs 80w90 (Better Gear Oil Selected)

Did you know that the wrong choice of gear oil can lead to premature wear and tear in your vehicle’s engine, potentially costing you thousands in repairs?

It’s a common misconception that all gear oils are created equal. But the truth is, the difference between 75w90 and 80w90 gear oils can be the difference between a smooth ride and a costly breakdown.

75w90 and 80w90 gear oils might seem similar at first glance, but they serve distinct purposes, especially under varying temperature conditions. If you’ve ever been confused about which one to choose or wondered about the real differences between them, you’re not alone.

The main difference between 75w90 and 80w90 is that 75w90 has a higher viscosity level than 80w90. 75w90 gear oil is ideal for axle operating at a higher temperature to inhibit premature depreciation.

Keep reading for more insights into the difference between 80w90 and 75w90:

  • The information will also help you avoid using these gear oils interchangeably.
  • You’ll get to know which lubricant oil is suitable for differentials and transmission.
  • Which gear oil you should use for some specific scenarios or vehicle types.

Difference between 75w90 and 80w90 Gear Oils

Viscosity Level

80w90 gear oil has a higher viscosity than 75w90. The viscosity rating of gear oil is denoted by two numbers. The first number represents the oil’s viscosity at cold temperatures, where lower numbers indicate less thickening in the cold. The second number represents the oil’s viscosity at high temperatures, with higher numbers indicating less thinning in the heat.

Therefore, 80w90 gear oil is thicker at cold temperatures compared to 75w90 gear oil. This can provide better protection for moving parts during cold starts. On the other hand, 75w90 gear oil maintains its viscosity and offers reliable performance at higher temperatures.

Note that the choice between 75w90 and 80w90 gear oil depends on the specific requirements of your vehicle and the operating conditions it experiences. Consulting your vehicle’s manufacturer or a professional is recommended to determine the appropriate viscosity grade for your application.

Operating Temperatures

75w90 has stable and robust properties recommendable for all drive applications in the vehicle. The gear oil is tolerant to oxidation and thermal effects. It can tolerate high temperatures of about 300-350F.

80w90 is a more versatile gear oil. The mineral oil is suitable for both icy and extremely hot weather conditions. It is applicable for a temperature range of -20F to 400F. 80w90 is the best oil for winter and summer weather conditions.

80w90 has a higher rating than 75w90 due to its tolerance to both cold and hot conditions. But 75w90 is limited to higher temperatures to minimize premature wear and tear. The winner under this category is 80w90 gear oil.

Gear Oil Density

The density of 75w90 gear oil is about 0.86. It implies that the oil is thicker to provide ultimate protection against wear and tear at high temperatures. But gear oil with high density tends to be clumpy and downgrade the efficiency of drive applications at low temperatures.

The density of 80w90 gear oil is about 0.90. The oil has low density but can still provide ultimate protection to the gears. The thin gear oil is suitable for working under extreme conditions with low maintenance costs.

However, the density of gear oil is not solely determined by its viscosity grade, and it can vary based on the specific formulation and additives used in the oil. 

While it is commonly believed that 75w90 gear oil has a higher density than 80w90, this may not always be the case. The density of oil is influenced by various factors, and it is not directly tied to its viscosity grade. 

Therefore, it’s better to consider the specific product specifications and consult the manufacturer or professional sources for accurate information regarding the density of different gear oils.

Additive Properties

75w90 contains a specific adhesive that coats the gears to prevent premature wear and tear. These adhesives make the oil sleek, non-foaming, and reliable for heavy-duty applications.

The additives also make the axle tolerate extreme temperatures without lacking lubrication. 80w90 contains particular anti-wear and lubricating additives. These properties help to manage depreciation in all racing cars and other heavy-duty applications.

These additives have unique heat control properties. Both 75w90 and 80w90 are winners under this category. They are incredible for both heavy-duty and high-performance equipment. Thanks to the special anti-wear and lubricating agents.

Gear Oil Price

75w90 has a constant viscosity over a wider spectrum of temperatures. The oil is thicker in extremely high temperatures and thinner in low temperatures. These dynamic properties make 75w90 a little bit expensive. 80w90 has a low viscosity level regardless of the temperature change.

The oil is thin in both high and low temperatures fostering a higher depreciation rate. The constant properties make 80w90 relatively affordable. 75w90 is super expensive and worth the value of your money.

The gear has better ratings to emerge as the winner under this category. It is the best option for heavy-duty machines operating under higher temperatures to minimize wear and tear.

Applications and Use Cases

Here are some specific scenarios or vehicle types where one type of oil may be more advantageous over the other:

75w90 Gear Oil:

This gear oil is frequently utilized in manual transmissions, differentials, and transfer cases of cars, trucks, as well as heavy-duty machinery and equipment. 75w90 is particularly recommended for vehicles operating in cold temperatures since it has a lower viscosity and flows more easily at low temperatures. Additionally, 75w90 is beneficial for vehicles engaged in towing or hauling heavy loads, as the oil offers enhanced protection against gear wear and tear.

80w90 Gear Oil:

This type of gear oil is commonly employed in older vehicles and machinery due to its higher viscosity, which provides superior gear protection. 80w90 is also well-suited for vehicles operating in hot temperatures, as it has a higher viscosity and is less likely to break down under high temperatures. Heavy-duty trucks and off-road vehicles often use 80w90 gear oil because it offers better safeguarding against shock loads and extreme pressure.

In general, 75w90 gear oil is a good all-around choice for most vehicles. It has a good balance of viscosity, load-carrying capacity, and resistance to oxidation and foaming. However, if you have an older vehicle, operate your vehicle in hot temperatures, or tow or haul heavy loads, then 80w90 gear oil may be a better choice.

Understanding Gear Oil Ratings

The gear oil ratings are determined by the numbers, which represent the viscosity or thickness of the oil at different temperature ranges. The viscosity directly impacts the oil’s ability to flow and provide effective lubrication for the gears. Here is a breakdown of the number system:

Viscosity Grade

The first number preceding the “w” (winter) indicates the oil’s viscosity at low temperatures. A lower number signifies a thinner oil that flows better in cold conditions. For instance, 75w oil is thinner at low temperatures compared to 80w oil.

Temperature Range

The second number following the “w” denotes the oil’s viscosity at high temperatures. Higher numbers indicate thicker oil capable of enduring higher temperatures without excessive thinning. For example, 75w-140 oil is thicker at high temperatures compared to 75w-90 oil.

Can You Mix 75w90 and 80w90?

The question of whether you can mix 75w90 and 80w90 gear oils is a topic of debate. While some sources suggest that it is generally acceptable to mix these oils as they do not contain additives that would significantly affect performance, our stance is that we generally DO NOT RECOMMEND mixing different types or grades of oil without proper guidance. 

To ensure the best performance and compatibility for your specific vehicle and application, we advise you to consult your vehicle’s manufacturer manuals for guidance on mixing gear oils.

Is 75w90 better than 80w90?

The choice between the two viscosity grades depends on factors such as the specific requirements of your vehicle and its operating conditions.

While 75w90 is mentioned as being suitable for high temperatures, consider the recommendations provided by your vehicle’s manufacturer. 

Ultimately, consult your vehicle’s owner’s manual or contact the manufacturer for the recommended viscosity grade for your particular vehicle.

Manufacturer Recommendations

To ensure that you’re using the right gear oil for your vehicle, check the vehicle’s manual or consult the manufacturer’s website. The manual will provide specific recommendations for the type of gear oil that should be used, as well as the viscosity and performance specifications. These recommendations are based on the design and engineering of the vehicle, as well as the operating conditions that the vehicle is likely to encounter.

Questions From Carowners

Which is better: 75w90 or 80w90?

Both 75w90 and 80w90 are viscosity grades for gear oil. The preference between 75w90 and 80w90 depends on the specific requirements set by your vehicle’s manufacturer. Consult your vehicle’s owner’s manual or visit the manufacturer’s website to determine the recommended viscosity grade.

Can you use 75w90 instead of 80w90?

In general, it is recommended to adhere to the viscosity grade specified by your vehicle’s manufacturer. However, there may be cases where using 75w90 instead of 80w90 is acceptable if the manufacturer allows for a range of viscosity grades. 

Nonetheless, it is essential to consider that using a different viscosity grade might impact the performance and protection of your vehicle’s gears. If uncertain, it is best to consult your vehicle’s owner’s manual or contact the manufacturer for guidance.

What happens if I made a mistake and used 75w90 instead of 80w90?

Using 75w90 in place of 80w90 could result in slightly altered lubrication properties, as the viscosity at high temperatures may be marginally lower. This could potentially influence the performance and protection of your vehicle’s gears. 

However, the disparity between 75w90 and 80w90 is relatively small, and in many instances, the impact may be minimal. To ensure optimal performance and longevity of your vehicle’s gears, follow the manufacturer’s recommendations.

Final Takeaways on 80w90 vs 75w90

75w90 has a higher viscosity level than 80w90. Higher viscosity gear oils can tolerate higher temperatures than lower viscosity gear oils. 75w90 oil provides maximum protection to gears against wear and tear.

But 75w90 gear oil becomes clumpy at lower temperatures and downgrade the performance of the gears. The best option under this circumstance is 80w90 gear oil.

The lubricant oil can withstand icy and hot conditions. Both 75w90 and 80w90 gear oils are the best to consider. These oils guarantee maximum protection to drive applications against premature depreciation. But 80w90 gear oil is less effective in providing protection when the temperatures are high.