4 key difference between 75w90 and 75w140 gear oil

So you’re looking to choose a gear oil? Well, just because your car manual says the stock type is the best for your vehicle doesn’t mean that it’s right for you. Over time, modern manufacturers have changed their cars to require different types of oils that are better suited to their needs.

It is not difficult to understand the difference between 75w90 and 75w140 gear oil once you know what they are talking about. Depending on the viscosity grade, the oil might either be thick or thin. It is also more difficult to flow if it has a larger number.

Below is a table of comparison between 75W90 vs 75W140 gear oil:

Oil viscosity at low temperatureSameSame
Oil viscosity at high temperatureThinnerThicker
Fuel economyBetterGood
Liquid Volume1 Quarts1 Gallons
BrandMobil 1Lucas Oil

75w90 Vs 75w140 Gear Oil: quick reviews

Before we make a differentiation between two of them, we need to know what they are and their specification.

These two oils come from either a synthetic or mineral base. Mineral-based oils are generally used for colder climates while synthetic oils are better for warmer climates.

Mobil 1 104361-UNIT 75W-90 Synthetic Gear Lube

Understandably, Mobil 1 104361-UNIT 75W-90 Synthetic Gear Lube can be a blessing for cars because of its outstanding features. It is made of synthetically integrated crude oil and refined, with the capability of being assembled in such a way that it has excellent performance.

One of the best parts about this type of gear lubricant is that it has perfect viscosity for most car models, which means that there is no need to worry about under-filling or over-filling.

It is assembled in such a manner that it has praiseworthy features, including being less viscous, more resistant to oxidation and shearing, and providing increased thermal stability. The blend of chemicals used in the production process results in the product having improved resistance to many chemicals as well as superior protection from water contamination.

Mobil 1 104361-UNIT 75W-90 Synthetic Gear Lube is an economically affordable lubricant. Thermal stability and oxidation stability, a chemical process that occurs when the lubricating oil comes into contact with oxygen, are two of the properties of this gear oil, which has a viscosity of 75% by weight and is very heat resistant.

It has low volatility which ensures low evaporation loss in high temperatures, offers excellent lubrication in extreme conditions, and can withstand high-speed rotation for longer periods than other oils.

75W90 is a high-quality gear oil that is primarily used in axle and transmission gears. The high Viscosity Index (VI) characteristic makes it easy to handle when pouring and less likely to air out over time. This low-temperature fluid has very low pour points, making it an excellent choice for cold climates.

What We Like?

  • Capable to provide excellent performance
  • Almost perfect velocity for most of the cars
  • It has improved resistant
  • It has a high-velocity capacity which is easier to handle
  • Low-temperature oil to withstand the cold weather

Things to Improve

  • You can lose 6-8% HP in the rear-end
  • Cannot give you high speed withlow friction

Lucas Oil 10121 Synthetic SAE 75W-140 Gear Oil

The gears in your truck’s drivetrain take a lot of abuse from heat, friction, and vibrations. Lucas Oil 1012175w140 is a synthetic gear oil that satisfies the challenging operating standards, including Scania STO 1:0, Scania STO 2:0 A, and API GL-5. It includes a built-in sealant that helps keep moving gears clean and provides the necessary lubrication to prevent overheating and unnecessary wear.

The product has been tested under extreme conditions to meet or exceed these standards. It has also been engineered with engine efficiency in mind to help keep your truck running smoothly for years to come.

Lucas Oil 1012175w140is engineered for use in heavy-duty, high load-bearing gears. It is used in engines where it lubricates the gears, bearings, and other moving metal parts in transmission or differential.

This gear oil is designed with a higher viscosity to help insulate the gear’s operation – which requires less energy to operate – and has a load-bearing capacity that is 20% higher than conventional gear oils.

Gear oil 75w140 is a synthetic stock oil developed with the help of synthetic additives combined with well-developed addictive and preservatives.

It furnishes some crucial and significant benefits that mineral gear oils lack: improved heat and wear resistance, non-toxic, and can resist oxygen and ozone better than petroleum oils. These qualities make it an excellent choice for those who do not want to compromise their safety or environmental responsibility in their machines.

What We Like?

  • Suitable for heavy-duty use
  • Capable to provide high speed
  • Low friction oil to enhance performance
  • Nontoxic oil safe for the environment
  • High on fuel economy

Things to Improve

  • Ensure first whether it is compatible with your car
  • You may need slip additive
  • There are some complaints about the gear noise issue

4 key Difference between 75w90 and 75w140 Gear Oils

A common question for many drivers is which type of gear oil is the best. This comparison will describe some of the differences between 75w90 and 75w140 gear oil to help you decide what will work best for your car.

1. Velocity comparison

When considering high viscosity lubricants for gears, it is important to understand that these types of oils are ideal for machines that run at low speeds and where the oil needs to stay on the surface of the metal. In other words, high viscosity gear oil is not designed for use in applications where there is a lot of friction or speed.

The need to reduce friction and increase efficiency for appliances and vehicles has led to the development of low viscosity synthetic oils that are thick at cold temperatures and thin when heated. These oils lack the shearing or thickening properties of mineral oil but provide excellent cooling due to their increased latent heat.

If you are a more visual learner, here is a videos about How To Read Gear Oil Viscosity Numbers on YouTube.

2. Fuel Economy

Both different weights of oil are designed for specific service needs, but where the 75w140 is a heavier viscosity and is used for more inflexible and rigid services. It’s only recommended for heavy-duty towing and regular use. Using 75w90 for regular maintenance is a good idea.

It is well known that the thinner viscosity of 75w90 fluid is typically used for normal services. However, there are instances where the heavier viscosity of 75w140 fluid should be used.

If you are experiencing inflexible and rigid services, you should opt for this heavier viscosity. This type of oil is only suggested for abundant towing or constant usage but can offer better protection in these circumstances.

3. Functional Temperature

The 75W140 is much thicker than the 75W90 at working temperature, which is the primary difference between the two alloys. At room temperature, their densities, on the other hand, will be comparable. The 75w90 oil is more suitable for gasoline engines, while the 75w140 oil is better suited for diesel engines.

4. Pricing

Hey, we’ve analyzed two internal or typed fluids that are used for different purposes. The first is 75w90, which is the more cost-efficient of the two, costing 12 bucks a quart (even though it can be considered at a higher price point).

It’s used for regular lubrication and moving parts like the engine. On the other hand, 75w140 is at a stronger viscosity and has a higher boiling point which costs 2 bucks a quart.

75w140 and 75w90 gear oil similarities

Both the oil have the same viscosity at low temperatures, but they differ in how they behave at higher temperatures. At high temperatures, the thicker, heavier oil is more likely to form deposits on engine surfaces.

The thinner, lighter oil is more prone to evaporate or break down into particles that can lead to engine wear even if it doesn’t form deposits.

How to Choose the Best Gear Oil?

Some people might think that all gear oils are the same. You might even think that choosing a gear oil is as simple as going with the cheapest brand available. However, a great deal of thought and a desire for quality should go into your decision to buy a gear oil.

Not every gear oil is alike and you’ll want to make sure it meets your needs, or else you might end up buying more than one.

There are many different types of gear oils for vehicles on the market today, but not all are created equal. Plus, three things should be considered when choosing a gear oil: viscosity, anti-wear properties, and stability.

Many lubricants on the market are labeled high-viscosity, but there are few differences between them. The higher-viscosity oils are best for low-speed, loaded gears operating in a dirty or rough environment.

These types of lubricants provide a thicker film that offers more wear resistance and will resist deformation of the gears under load.

I will elaborate on the benefits of higher viscosity oils in gears that are subject to heavy loads and high speeds. Higher viscosity provides a thicker film, has higher wear resistance, and less deformation of the gears as compared to lower viscosity oils. The film is thicker because it cannot be squeezed out as easily by the pressure between gear teeth.

Many people have a misconception that low viscosity oils are worse for high-performance cars. These people often think that low viscosity oils are not vicious enough to provide adequate lubrication or protection to the engine and that they will burn quicker than higher viscosity oils, but this is not the case.

Low viscosity oils may be better suited for systems where there is not as much pressure and friction as in other systems.

In comparison to high viscosity oils, low viscosity oils are best for high-speed systems with lower loads. Low viscosity oils have a better ability to keep up with the high-speed demands in these types of systems.

This is because low viscosity oils allow motors to run cooler and at a higher RPM, which in turn reduces friction and wear on the bearings.

Relevant posts:

closing Thoughts

Many vehicles these days are recommended to run on a 25w50 oil, while higher-performance vehicles might need the 75w140. However, many passenger vehicles are recommended to use 75w90 oil. This type of oil is ideal for everyday passenger vehicles, which can be used to haul heavy loads or travel long distances without worrying about damaging their engine.

In conclusion, you should understand difference between 75w90 and 75w140 , and choose based on the environment in which you use your vehicle. The lower viscosity of the 75w90 makes it better for drier climates where it can be changed more often because of the higher heat. The higher viscosity of the 75w140 is perfect for cold weather, wet conditions, and vehicles that are not driven every day.

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Mahir Ahmed


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1 thought on “4 key difference between 75w90 and 75w140 gear oil”

  1. Excellent article. I drive a 1999 Dodge Dakota, 2.5L 4 cil, and.. i was thinking about changing the rear diff oil, but.. thinking about mix, 1 bottle of 75w90, and 1 bottle of 75w140, is it possible? i don’t use the car everyday, also, not carry heavy loads..


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