best differential fluid

Top 10 Best Differential Fluid to Buy in 2021

Have you forgotten to check on the gear oil again? I cannot blame you there. With so many things to maintain in a four-wheel vehicle, even a skilled driver overlooks this part.

Do not worry. I am here to remind you of that unnoticed significance. Of course, every product – small to substantial – has so many brands backing them up it is hard to find the hidden gems.

Yet, they are waiting in the store isles for you. Differential fluid is no exception. You have to pick the right lubricant for the axle gear to function.

What is the best differential fluid in your case? Let me walk you through it in the section below. First, how about a little clarification on the topic?

Need A Quick Decision? Here’s My Top 05 Picks

Does Changing Differential Fluid Make a Difference?

Pretty sure many rookies have had this question popping up in their minds. Yes, it is critically necessary to change the oil, but why? Continue reading.

What is a Differential?

First, it assists the wheels in rotating in pairs as you drive. Second, it is a component that delivers torque from the engine to the wheels. Third, it allows various speeds at angular rotations. In short, you will constantly face fishtails without a differential.

Now what you have to consider are the differential gears. Yes, there are a bunch of them. Where there are gears, there ought to have lubricants. Hence, it makes a great deal of a difference once you replace the old fluid.

Benefits of Differential Oil Change

I have plenty of points to indulge you with but let us stick to the primary advantages. They will help you understand your vehicle better.

1. Controlled Thermal Activity

A machine tends to get hot whenever it runs for a while. Now picture a vehicle you drive toils on hundreds of complicated metallic components.

It heats the internal functions, which have no way of regulating unless you apply the gear oils. So, it is necessary to replace the fluid timely.

If you do not want to experience the terrible burning smell emitting from the gearbox, you should follow the replacement interval accordingly.

2. Smooth Assemble

There is an indescribable satisfaction when you magnificently make the perfect turn or drive to a corner. You will not be able to feel it if you forget to change the fluid.

Remember that these gears inside the differential go over constant friction. The heat elevates, and the pressure is too much.

However, keeping the diff fluids in check will protect the overall operation in the housing. Even if the component metals have persistent contacts, the assembly will not break.

Therefore, the vehicle will gain a healthy differential (axle) element that delivers a vibration-free driving experience. Say goodbye to the fishtail disaster!

3. Prevents Damage

By now, you have gathered that continuous friction made by metal-to-metal contacts results in increased heat.

If the lubricant amount reduces to a dangerous level, there is a high chance of damaging the gears. So, this fluid is a savior to many small parts. It will keep the grinding to a minimum and provide corrosion protection.  

Next time, inspect the axle section too when you pry into the engine functionality.

Top 10 Best Differential Fluid Reviews in 2021

Here are the most demanded differential fluid products with honest reviews for each. Shall we begin the journey?

1. Red Line (50304) MT-90 75W-90 GL-4 Manual Transmission and Transaxle Lubricant – 1 Quart

We always seek the perfect product at a reasonable price for maintenance. Red Line MT-90 has made sure you do not have to look anywhere else.

It is the best gear oil for differential that offers low sulfur formula. As a result, the lubricant is less slippery and provides the right viscosity.

This GL-4 gear fluid is quite popular for Toyota, Nissan, Mitsubishi, Audi, Mazda, etc., transmissions. And we all know how significant it is for the gears. Its compatibility is what I love the most.

Do you know why? It prevents frictional damage efficiently and quickly. If the gear-change shows notchy issues, this lubricant is a way to get out of that situation, too.

The cold will not bother you anymore because of the Red Line MT-90 heavy-duty gear oil. It is the ideal choice that provides high-end differential component protection.

Highlighted Features:

  • Low in sulfur; suitable for brass synchros
  • Reduces cold, notchy shifts
  • Satisfies 75W90, 80W90, 90 gear oil viscosity
  • Suitable for GL-1, 3, 4 applications
  • Adaptable to high or low mileage vehicles

2. Genuine Honda Fluid 08200-9003 VTM-4 Differential Fluid – 1 Gallon Bottle

Do you own a Honda model? Are you unsure which gear lube to apply for that precious vehicle of yours?

I had to go through something similar, but not anymore. The Genuine Honda VTM-4 fluid is a product that never disappointed its users.

After thorough research, the brand has developed this fluid for the Honda differentials alone. It can replace the OEM fluid and not even compromise the authenticity.

You no longer have to guess whether it will work or not. With Genuine Honda fluid, there is no risk involved. It allows the gear tooth to work in sequence, eliminating chances of grinding at the rear end.

If your Honda is close to schedule for the differential fluid replacement, how about trusting Genuine Honda this time? 

Highlighted Features:

  • Quick fix lubricant for rear-end diff
  • Ideal for Honda vehicles only
  • Compatible with high temperature
  • Perfect consistency for long-term operation
  • Meets all the Honda quality standards

3. Lucas Oil 10048 SAE 75W-90 Synthetic Transmission and Differential Lube – 1 Gallon

Have you ever faced the existing fluid forming foaming substance? Then Lucas Oil 10048 can resolve such an issue. This is a GL-5 differential lube that is also suitable for transmission.

The super slick lubricant consists of special antiwear additives. If you operate your vehicle under extreme pressure or in a harsh environment, I suggest opting for this product.

It has a 100% synthetic formula that prolongs the lubrication even when the temperature is high. The additive ensures protective cushioning during turns and corners.

This stuff works like magic, eventually eliminating the hesitation you experience on initial acceleration. If you want my opinion, this GL-5 Lucas Oil is incomparable to anything else in the market.

Besides, you will not have to apply the additive if the rear differential is not under extreme grinding conditions. 

Highlighted Features:

  • Resists high temperature
  • It contains a special additive package
  • Prevents foaming
  • Superslick for heavy-duty performance
  • Resists squeeze-out situations in gears

4. Motul Gear 300 75W90 Synthetic Transmission and Differential Fluid – Liter – 2 Pack

The next on the list is the Motul Gear 300. It is a 75W90 synthetic fluid that can make a difference you will not expect. Many users apply this gear oil to replace the factory oil.

It is an excellent product that offers reliable protection for the front and rear differentials. Just make sure you follow the precise intervals before replacement.

There are two packs within budget; you will not have to search the whole market for the perfect consistency so long you have Motul Gear 300.

The synthetic oil lets the gears work under severe pressure. It makes sure the gearbox does not face complications like corrosion, wearing, frothing, etc.

In short, it is the name that comes to my mind when maintaining a sports car. You know how powerful these vehicles are, and regular GL-3 or 4- lubricants do not apply to them.

So, if you possess such a specially developed vehicle that goes through heavy pressure, this formula is ideal for it. The constant friction will reduce due to the remarkable viscous quality.

Highlighted Features:

  • Developed for high-pressure-enduring vehicles
  • 100% synthetic
  • Anti-corrosive and antiwear
  • Prevents frothing
  • Diminishes frictions

5. Polaris Premium Synthetic AGL Plus Gear Lube 32 oz / 946 ml

We all know Polaris vehicles are quite the charm, whether it is a quad bike or a slingshot. These rides deserve the best gear lubricant formulas for the differentials.

The Polaris Premium AGL Plus is such an example a Polaris owner cannot avoid. So, if you wish to protect the internal ATV transmission components, I cannot think of a better product than this one.

Its viscosity is so perfect that it sets to work on the preventative measures of wear and rust. We all know how terrible the outcome can be if you don’t take care of the chain and gear corrosion.

In short, that Polaris model will run without a notch as you apply this gear lube. It gets the job done when oxidation is in question. You can rely on synthetic oil without spending much on the product.

Highlighted Features:

  • Minimizes wearing
  • Reduces friction by providing a film protection
  • Ability to handle high-temperature level
  • Protection from rust, corrosion, oxidation, foaming
  • Offers shock protection

6. Bar’s Leaks 1816 Differential Gear Repair

Suppose you already own the gear oil for noisy differential, but it requires a particular additive. Bar’s Leaks 1816 can be the answer you are looking for.

This is a treatment additive that works with pretty much any gear oil, whether it is synthetic or conventional. It is a suitable repairing additive that is highly recommended for heavy-duty gear lubes.

Once you add it to the formula and apply it, you will notice a significant improvement in the noise department. Plus, no more leaks, froths, wear, or corrosion can be noticeable either.

It contains sulfur, nitrogen, and phosphorus to deliver metal-to-metal protection. Hence, the gears will stay intact for a long time due to the reduced frictions. You can finally be free of all the chatters caused by the limited-slip axles.

While it works excellently at high temp, the additive flows even at low temp.  

However, remember to follow the instruction before mixing, though. Overfilling can damage the components.

Highlighted Features:

  • Seals leaks
  • Reduces noise, wear, temperature due to EP and AW
  • Minimizes friction
  • Increases performance even at low temperature
  • Assists in manual transmission shift

7. Valvoline High Performance SAE 75W-90 Gear Oil 1 QT

So, you are looking for a gear oil for limited slip differentials, you have come to the right place. Valvoline is a reliable brand for many vehicle owners who hardly switch this product for another.

Do you know why? It is a GL-4 or 5- specified formula that shields the gears from wearing and scuffing. Suppose the limited-slip hypoid differential in your vehicle is acting up.

Can you trust just about any gear oil from the store? Of course not; therefore, the Valvoline ensures you do not lose your mind searching for the right lube everywhere.

So, the application will shield every component from severe temperature, providing long-term durability. It does not matter if yours is a sports utility vehicle, passenger car, or light/heavy-duty truck.

The 75W90 will suit them all based on the API rating. It is like owning all-in-one differential lube! Besides, it prevents shock loads.

Highlighted Features:

  • Recommended for hypoid differentials
  • Suitable for non-synchronized manual transmissions
  • Protects against scuffing, pitting, scouring, corrosion, etc.
  • Specifically for API GL-4 and GL-5
  • Withstands shock loading and severe temperature

8. Castrol – Syntrax Long Life 75W-90 Differential Fluid

The Castrol – Syntrax is a synthetic differential gear oil 75w-90 that is unique from the standard lubes. It is a super-effective formula for your BMW.

If yours has non-limited slip rear axles, this is the perfect solution for the cause. The entire 1L content has the viscosity ideal for the particular gear units. It is almost as if you have the BMW gear oil.

The specifications are pretty similar but deliver better outcomes at prolonged service life. Just make sure to insert the right amount for your vehicle.

Otherwise, you will love the uninterrupted smooth performance as you make a solid turn. There is just one little problem. The flipping tube might not fit the cap.

You can use a large syringe to avoid spills. Overall, it is worth your time and money.

Highlighted Features:

  • API rating is GL-5
  • Suitable of BMW non-limited slip
  • Adaptable to various high-low temperature
  • Excellent viscosity for BMW diff
  • Extends service life

9. Royal Purple 01300 Max Gear 75W-90 High Performance Synthetic Automotive Gear Oil, 1 Quart (32 Ounces)

There is almost nothing we will not do to run those gears smoothly in our vehicle. The issue where we get stuck is at the brand or product selection.

It is a pain just working on guesses! However, royal purple gear oil will eradicate such hard work and make things easier for you. This is a heavy-duty synthetic front and rear differential fluid, with API GL-4 and 5- specified.

Thus, whether it is a truck or an RV, the result will be impressive. You can say goodbye to the corrosion and intense frictions/grinding. The product is engineered to stabilize the temperature and increases the HP.

It is nothing like the ordinary formulas. You will feel the power maximization as you drive. This means the gear oil can meet the requirements the differentials need.

Who would not love to have a better gas mileage advantage?

Highlighted Features:

  • Includes hypoid friction modifier additive
  • Offers corrosion protection
  • Rapid separation from water
  • Powerful viscosity extends gear and bearing lifespan
  • Maximizes horsepower and smooth gear functions

10. Millers Oils CRX LS 75w90 NT+ – 1 Liter Bottle

Are you looking for a rear differential fluid with EP additives? Then you know where to look!

Honestly, I was not expecting much from Millers Oils at first. Nevertheless, the viscosity quality of this product has changed my mind. Besides, it offers anti-shock properties.

The fully synthetic gear oil comes with friction modifiers for limited slips. Furthermore, it is a superb choice for competition gearboxes, hypoid differentials, synchromesh, or non-synchromesh.

You will notice a significant reduction in temperature after the application. The outcome is the smooth and quiet turns every time you hit a corner. Besides, it will increase the performance due to the all-around mechanism protection.  

So, are you ready to take that ride for a spin? This time I assure you it will not cause a problem as you shift gears. Of course, it will continue to prevent oxidation and corrosion so long you follow the replacement interval.

Highlighted Features:

  • It consists of nanotechnology EP additives
  • Compatible with GL-4 and GL-5
  • Includes anti-shock properties
  • Stabilizes thermal activity and oxidation
  • Ideal for limited slips  

Comparison Table of Top 5 Differential Fluid

NameAPI RatingFluid TypeLiquid VolumeLimited Slip Compatibility
Red Line (50304)GL-4Synthetic946mlNo
Genuine Honda Fluid 08200-9003NilVTM-43.785mlNo
Lucas Oil 10048GL-5Synthetic3.785ml & 946mlYes
Motul Gear 300GL-5Synthetic1000mlNo
Polaris AGL PlusNilSynthetic946mlNo

Differential Oil Types

If you did not know it before- you would see two types of differential oil at the store. Which one is better?

Mineral Oil

Do you drive an older model vehicle? Is the budget tightly packed? Then opting for mineral oil is the way to go.

It is a refinement of crude petroleum. It contains impurities and hydrocarbons in the raw form. Of course, the one you see in the market is free of it all. However, it still leaves mild traces of the contaminants.

On the other hand, mineral oil is the most common choice at a low price. It has a higher viscosity which causes slow flow. You might have to replace it more frequently.

Synthetic Oil

If there is a better version than mineral oil, then you can rely on synthetic. Although it may not be the best answer to old vehicles, it contains fewer impurities.

Thus, this type of lubricant is best suited for modern vehicles with powerful engines. They maintain the performance to an optimum condition.

Synthetic gear oil has to undergo complex alteration to deliver finer results. It offers stable consistency and provides less replacement.

While it is slightly overpriced, it sure can protect the gear components from wear and corrosion.

What is the Best Option?

Frankly speaking, you cannot choose between the two differential fluid types. Do you know why? Each vehicle is cared for differently, even when the pinion and ring gears are similar.

If your vehicle manual says mineral oil, then you find the best one. The same goes for the synthetic.

Things to Consider Before Buying

You have to know a few basics before buying gear oils. It can resolve confusing purchases to a minimum.

1. Consistency

Differential fluid has a higher viscosity than engine oil. Thus, your car manual must have a reference for the information.

This consistency and density of the gear oil have a major role in keeping everything in place without damage. If you cannot find information regarding a specific model, you can check online.

Sometimes the differential fluid selling stores or service centers can help you pick the right product.

2. API Rate

The API rating shows the consistency grade of oil that is appropriate for a vehicle. It helps the driver aim for a suitable fluid for a particular type of gear in the motor.

This rating depends on the differential condition. There are thousands of various automobile types, and they all have different ratings.

We usually classify them as GL (Gear Lube) with a grade digit associating with it. The GL ranges from 1 to 6, being 6- as the most pressure-bearing sustenance.

For example, GL-1 gear oil is suitable for operating modes that are light. It is quite straightforward. Most standard car/truck owners opt for either GL-1, GL-2, GL-3, or GL-4.

In contrast, if you are looking for differential fluid for jeep jk that runs in a rough environment, GL-5 or GL-6 is the way to go.

There is no classification of vehicles to tell you the truth. The API rating characterizes the types of gearboxes, operating conditions, torque conditions, and shock load to determine what you require.

Thankfully, your vehicle manual will have this data, so you will not have to wreck your brain wondering what to get. However, it might vary depending on how and under what circumstance the vehicle performs.  

3. ANSI/AGMA Standard

Surely, you will find this information in the manual as well. Still, let me explain what this indicates.

It tells the gear tooth tolerance correlation with the gear accuracy level. In short, you will understand what grade differential fluid you ought to get by having a look at the details.

Do not forget to check the required standard, as it might save the components from severe frictions and grinds. And it is possible to damage the rings and pinions by using the wrong gear oil.

4. Additive Types

Since the fluids are graded, it is evident that some might contain more or less special additives. However, there are three important ones that are mostly sought out.

The R&O additives are for those who are facing corrosion. It protects the gears from heavy-duty oxidation and rust. Plus, it can resist other chemicals too.

Complex additives increase the lubrication properties and apply a highly protective layer to the gear components.

Lastly, it is the anti-scuff additive. It is similar to the complex additives, but the lubrication coating is relatively durable. The film it creates can last a long time.

Besides, there is the EP additive that you can apply only if the gear parts are wearing down quickly. It can happen when the lubricant fails to provide a protective film under heavy pressure.

Frequently Asked Questions ( FAQs)

1. How often should I replace the differential oil?

Answer: The maintaining guide usually indicates rear differential fluid replacement after every 30K to 60K miles. Mileage may vary according to vehicle models/type and operating conditions.

You should still confirm it from the car manual or a skilled mechanic.

2. Is synthetic oil better than regular gear oil?

Answer: Since the mentioned oil does not age even at high temperatures, it will deliver prolonged service. Moreover, it has better barrier film and reliable viscosity.

3. When should I use API GL-4 or 5- differential fluid?

Answer: That depends on the operating conditions in driving. Is it severe? Does your vehicle go through heavy impact load almost frequently? Is the environment in your region force the vehicle to operate under extreme pressure?

If such are the issues, then API GL-4 or 5- will aid the differential to maintain continuous friction load. The high consistency gear oil will lubricate the component and prevent the heat from getting out of control.

4. Can I mix synthetic diff lube with conventional ones?

Answer: There is no problem mixing both types of oil. However, this method might reduce the synthetic’s superiority. It is possible to face detracted performance regarding the benefits. It will not cause harm to the differential, though.

5. Can I use transmission oil for the differential?

Answer: No, you must never attempt that. Even though lubricants pretty much appear similar, there is a reason for such categorization. Differentials have mechanisms that require a specific type of lubricant.

Transmission fluids do not fulfill that necessity. Nevertheless, you can apply gear oil for manual transmission.  

Final Words

When you own a vehicle, you have to be committed to its needs and care. Do not forget to replace the gear oil at a given interval.

Sometimes the lubricant can have water contamination. You should keep an eye on that too. Otherwise, stick to the schedule.

Furthermore, prepare to have a messy area if you plan to change the oil in your place/garage. Keep a wide container under the rear bumper to collect the old lubricant.

At the end of the day, we all wish for our vehicle to be in peak shape. But it is quite an easy task overall. So what is the best gear oil for differential, in your opinion?

Hence, you should have the upper hand here. Now go out and take that ride for a groove. See you!

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