When you use gear oil regularly on your vehicle, you prevent malfunctions in your transmission, drive axles, and gears. The gear oil grade needed for your car depends on the conditions.
Take, for example, the Ford Mustang you drive. Depending on how hard you drive or tow, the manual of your car may recommend 75w90, while others recommend 75w140. Can you tell me how 75w90 differs from 75w140?
It compares 75w90 vs 75w140 from the perspective of viscosity grade, performance, fuel economy, and application characteristics. As well as showing how certain grades affect Mustang, BMW, Subaru, and other make and model performance, I will demonstrate how they work.
How do 75W-90 and 75W-140 gear oils differ?
There is a significant difference in operating temperature between 75W-90 and 75W-140 gear oils.
Oils with 75W-140 viscosities are thicker than oils with 75W-90 viscosities. An oil quantity flows through an opening in 140 and 90 seconds, respectively. A 140ml sample passes through 75W-140 in 1 second while a 90ml sample passes through 75W-90 in 90 seconds, indicating a variably viscous solution.
There is no difference in density between the two oils. The viscosity of 75W-90 is lower at higher oil temperatures than 75W-140. However, at low oil temperatures, they have the same thickness. Your vehicle requires further investigation in order to determine the best gear oil for it
75W-90 Gear Oil
In 75W-90, artificial crude oils are combined with refined extra skim to form a synthetic gear lubricant. Rail gearboxes usually use this type of gearbox because it can handle heavy loads.
Heat and oxidation stability are among the best attributes of this synthetic gear oil. Low pour points and good stability at low temperatures are some of its outstanding characteristics. Viscosity index (VI) is excessive and pour point is low.
75W-140 Gear Oil
An engine lubricant such as 75W-140 is formulated for heavy-duty operation, making it suitable for use in drivetrains. For heavy-duty trains, it needs to be well insulated, able to bear loads of a great deal of weight, and stable.
The synthetic gear oil outperforms mineral gear oils due to a combination of synthetic base oils, superior additives, and preservatives. This material exhibits excellent resistance to corrosion, heat, and oxidation over a wide temperature range.
What’s the difference between 75w90 and 75w140?
Grading of viscosity
When oil temperatures are higher, 75W-90 is thinner
As I said, thicker oil is better in hot weather, which is why the number after W will be higher. The films formed by a 75w90 oil would be thinner than those formed by a 75w140 oil at high temperatures. If you live in a hot climate, 75w140 is recommended for your car.
A 75w90 oil will lose its viscidity quickly if the vehicle hauls heavy loads, accelerates and brakes quickly back-to-back, or drives on the freeway for a long time. It is recommended that your vehicle be lubricated with a 75w140 grade gear oil if your driving pattern fits any of these descriptions.
Efficiencies in fuel
Fuel economy is better with 75w90 than 75w140.
Viscosity grades are thinner when the temperature is high. Additionally, additives may also affect this feature, as can add-ons and compositions used in the fluid. We don’t know what effects gear oil additive packages have in reality, because manufacturers don’t reveal much information about them.
Fuel economy differences are too small for most car owners to notice. Also, daily drivers aren’t affected by it.
Application
The viscidity of gear oil has most likely become more clear to you, and you now have the knowledge to pick the right gear oil. I have listed below the basic differences between the fluids as regards their application.
75w90
During low ambient temperatures, oil retains its viscosity longer than at higher temperatures. For passenger cars primarily used in city traffic or in winter conditions, 75w90 gear oil is ideal.
75w140
My recommendation would be to use 75w140 gear oil if you haul a lot of heavy loads, live in a hotter climate, or race. Despite its lower kinematic viscosity, the lubricant retains viscidity as the mercury soars, similar to 75w90 in the lower temperature range.
75W-90 vs 75W-140 Gear Oil Comparison:
| Aspect | 75W-90 Gear Oil | 75W-140 Gear Oil |
| Viscosity | Infrequent towing and regular service are suitable for this lower viscosity product. | For continuous use and severe towing, this product has a high viscosity. |
| Operating | Operating temperatures make it thinner. | When operating at high temperatures, it becomes thicker. |
| Temperature | At room temperature, the density is similar | At room temperature, densities are similar |
| Pricing | Approximately $12 per quart, lower cost | There is a higher cost per quart, about $20 |
| Ideal Use | Useful on a regular basis | Heavy-duty recommended |
Some cars and models are compatible with 75w90 & 75w140
Mustang 75w90 vs 75w140
The Mustang should be lubricated with synthetic gear oil, as recommended by Ford. Since modern Mustangs make a lot more horsepower, they use 75w140 gear oils instead of 75w90 fluids. Viscose fluids are therefore able to rapidly lower operating temperatures, reduce friction between mechanical components, and retain their lubricants for long periods of time.
75w90 Vs 75w140 BMW
A synthetic gear oil of 75w140 is recommended by BMW. In city situations, users may want to use 75w90 oil instead of this oil, which is suitable for heavy use. In order to maximize the life of the mechanical components, you may need to shorten the draining interval. Keep in mind that OEM recommendations are strongly recommended.
75w90 vs 75w140 Subaru
Depending on the climate where the vehicles are driven, Subaru recommends a different grade of synthetic gear oil. Users who live in hot climates can use a 75w140 fluid instead of the OEM-recommended fluid to extend their drain intervals and improve performance.
The Basics of Gear Oil
Across a wide range of temperatures, a grade indicates a difference in viscosity. The “W” indicates the fluid’s flowability at a colder temperature, or its winter suitability. Viscosity at low temperatures is indicated by the number before W. When your oil is at low temperatures, the number is lower. Hot weather viscosity is indicated by the number after W. High numbers indicate thicker oil at high temperatures.
Therefore, a 75wX fluid with an operating temperature of -40°C/-40°F has 150,000 CP, meaning it can lubricate mechanical components well below freezing temperatures. It is therefore important to use gear oils suited to low-temperature conditions.
In the second number, we have the fluid’s kinematic viscosity at 212°F/100°C. In terms of centiStokes (cSt), Xw90 oil has a hot viscosity range of 14 to 25 cSt. Xw140 ranges between 25 and 43 cSt. Since Xw90 lubricants thin out faster at higher temperatures, they are less effective.
Related Articles
75w90 vs 75w140: Pros and Cons
| Aspect | 75W-90 Gear Oil | 75W-140 Gear Oil |
| Fuel Efficiency | Generally better | Slightly lower |
| Performance in cold weather | Low-temperature flow is good | In cold weather, the flow may not be as smooth |
| Exceptional load capacity | Moderate | High |
| Resistance to heat | Moderate | Improved heat resistance |
| Heavy-duty suitability | Limited | Heavy-duty recommended |
Frequently Asked Question
What is the main difference between 75W90 and 75W140 oil?
The primary difference between 75W90 and 75W140 oil is their viscosity. At 100°C, 75W140 has double the viscosity of 75W90, meaning it is thicker and provides better protection against gear wear. However, this increased thickness can lead to higher power consumption in the drivetrain.
When should I use 75W140 instead of 75W90?
75W140 is typically recommended in high-temperature environments or for applications that require additional protection, such as towing heavy loads or in off-road conditions. It can help reduce wear in scenarios where the equipment is subjected to extreme stress.
Can using 75W140 oil cause damage to my vehicle?
Using 75W140 in place of 75W90 may lead to increased drivetrain losses due to its thicker nature, which could potentially cause issues in some vehicles, particularly if they are not designed for such viscosity. It’s essential to follow the manufacturer’s recommendations for oil viscosity to avoid any risk of damage to the gearbox or differential.
Will switching from 75W90 to 75W140 affect fuel economy?
Yes, switching to 75W140 can negatively impact fuel economy due to its higher viscosity, which can lead to increased friction and power loss in the drivetrain. For optimal fuel efficiency, it is generally advised to use the oil viscosity specified by the vehicle manufacturer, which is often 75W90 for standard conditions.
Is 75W90 sufficient for high-performance applications?
For many high-performance applications, especially in moderate temperatures, 75W90 is often sufficient. It provides good protection while maintaining lower power consumption. However, in extreme conditions or for high-torque applications, 75W140 may be beneficial for added protection.
Conclusion
A car’s specific needs and operating conditions will determine which gear oil to use, such as 75W-90 or 75W-140. A versatile 75W-90 Oil may be conflicting in high temperature conditions because it can be utilized in a variety of applications and environments.
75W-140 oil, on the other hand, is strong enough to protect high-powered vehicles from harsh weather conditions, though it may struggle in colder climates. In order to ensure efficient overall performance and durability of the vehicle’s transmission and gears over a wide range of operating environments, it is beneficial to understand the strengths and limitations of each Oil.
