Differential Fluid Vs Transmission Fluid (7 Reasons Which Is Better)

What’s better between differential fluid vs transmission fluid is a hot debate in most automobile forums and threads. One group of car campers said diff fluid is better. But another group said transmission fluid is better. 

But why do they claim this? Or Is there any valid reason? 

Simply, the purpose and functionality are the most crucial difference between diff and transmission fluid. When the diff fluid works great for manual gearboxes, the transmission fluid works efficiently on automatic transmission systems. 

If you are eager to know elaborately, get in touch with us. In this post, we’ll invest everything in detail under multiple parameters. 

Differential Fluid Vs Transmission Fluid Comparison Table

Knowing the key differences is the super shortcut way to get a grasp idea of the fluid differences. This comparison table will showcase all the basic information on both fluids for your convenience. Let’s have a birds’ eye view. 

Features	Differential fluid	Transmission Fluid
Types	2 types (Mineral and Synthetic)	2 types (Automatic and Manual)
Used for	Manual transmission	Automatic transmission
Thickness	Thicker	Thinner
Viscosity grade	70-80W-90/140	0W-30/40
Heat Resistance	Higher	Lower
Pressure handling capacity	Higher	Lower
Cleaning Capability	No cleaning ability	Super oil cleaning ability
Oil changing interval	50000 to 60000 miles	30000 to 100000
Compatible vehicles	Truck, Jeep, and any large vehicles	ATV, UTV, motorcycle, and most passenger vehicles

You must get a quick overview from the table, but that isn’t enough to determine which is better. So you should check the below words to enrich your knowledge about diff and transmission fluid. 

Overview of Differential Fluid 

Diff fluid is also known as gear oil, as its main function is lubricating the gearboxes to ensure better rotation during transmission. It also helps to cool multiple gears in the automobile. So the vehicle gears won’t lock up or break due to overheating. 

Since the oil contains sulfur to ensure proper lubrication, it looks slightly thicker than transmission fluid. You’ll even get a bitter smell like rotten eggs from the oil because of sulfur. 

Benefits 

• Faster lubrication in rear clutches, gears, and bearings
• Ensure the potential condition of your vehicle’s differential for a longer time 
• Offer the best handling in high-pressure and stressful situations 

Overview of Transmission Fluid 

The fluid which transfer power to the vehicle’s hydraulic parts or engine to support its transmission is called transmission fluid. It prevents internal parts engagement of the transmission system. So the transmission stays cool after running high mileage.  

The transmission fluid is thinner and can incredibly manage the higher temperature to use in harsh weather conditions. However, it looks green or red, which helps to differentiate it from regular engine oil. 

Benefits

• Great to use in cold weather
• Higher oxidation and thermal stability 
• Excellent control over vehicles’ frictional behavior 

A Detail Comparison of Differential Fluid vs. Transmission Fluid

After in-depth research, we have gathered vast knowledge about both fluids. Here, we discuss the results feature by feature.

1. Functionality

The fluid functional areas play an important role in understanding its importance on your engine life and impact its performance. The more engine area one fluid can cover, the more efficient and reliable that is for your driving experience. 

Differential Fluid

The diff fluid covers the manual gear systems of your vehicle and smoothly flows fluid from its driveshaft to the clutch.The clutch, pinion gears, teeth gears, bearing, and other parts get enough lubrication to offer better transmission while cornering or hauling your vehicle. 

Transmission Fluid

The transmission fluid activities are aligned with your vehicle’s automatic transmission system. This fluid flows to lube all the mechanical parts according to their requirements. Its most crucial work is to prevent rust, corrosion, metallic components friction, sludge and deposit formation. So that the engine will stay cool and the oil will stay clean even after running many miles. 

2. Viscosity

The thickness or viscosity of the fluid largely impacts your engine performance. It may get immature damage if your vehicle engine is deprived of enough lubrication due to too thick or too thin oil. 

Differential Fluid

Diff fluid comes in higher viscosity, as it has to work under high pressure and temperature. However, various viscosity diff oil is available in the fluid market. But diff oil’s average viscosity grade range is 70/80W-90/140. 

This higher viscosity also can handle higher temperatures, such as  200° to 250°f. So the diff fluid is good to use in hot weather, even midday. 

Transmission Fluid

Transmission fluid is thin and comparatively lower in viscosity grade. The available weight grade of transmission fluid is 0W-30/40, which is great to use in cold weather conditions. But that doesn’t mean you can’t use this oil in hot weather. As it can handle approximately 175° to 220°f temperature, it’s also good to use in high temperatures. 

3. Heat Resistance 

Most vehicle engines produce higher heat while running due to component friction. You can consider it as the engine’s internal heat. But, the hot weather fuels it and increases the heating level. It may damage your engine if the oil can’t withstand higher heat or won’t have good heat resistance. 

Differential Fluid

The differential fluid has more heat resistance than the transmission fluid. Because it can transfer the internal heat to the outside through its gearbox. Moreover, the diff fluid has great control over the ultimate heat of the engine. 

Transmission Fluid 

Because of the lower viscosity grade and boiling point, transmission fluid is less heat resistant than diff fluid. As your vehicle’s transmission system produces less heat than the gearbox system, this oil can manage the transmission system. 

4. Pressure & Stress Handling Capacity

Today’s engines have to handle more stress and pressure than older engines. So the higher the pressure can handle your fluid, the greater performance you can expect from your engine—even vice versa. So you can understand the impact of fluid on the engine performance. 

Differential Fluid

The diff fluid works on the front and rear differential while turning the vehicle at high speed. Higher the speed, the higher the stress. So, it’s easy to realize that it has to handle higher pressure and stress. Even the oil is formulated by keeping that in mind. 

Transmission Fluid 

Oppositely, transmission fluid works for lubes the internal engine’s components to prevent rusting and sludge formation. Yes, this oil can handle a mediocre pressure, but that is less than diff fluid. 

5. Cleaning Capability

The cleaning capacity of any oil is directly related to two major concerns. One is fuel economy, and another is the percentage of releasing emissions through the exhaust pipe. The more time the fluid stays clean, the less it consumes, and the less emission is released into the air. 

Differential Fluid

Diff fluid won’t have any specific additional detergents that can work to keep the oil clean after burning. So that the gear oil will gunk, milky, or cloudy earlier than transmission fluid. 

Transmission Fluid 

The transmission fluid has some additional additives. These help prevent oil from building sludge and deposits that are the culprits of turning the oil black and gunk. Even the oil won’t turn milky due to air exposure. 

6. Oil Changing Interval 

Oil changing interval is one of the crucial points for those car enthusiasts who like long driving. As if your engine needs oil in the middle of the journey, undoubtedly, that will ruin the pleasure of your tour. Moreover, nobody likes to change their vehicle engine oil frequently. So the high mileage oil is the best.

Differential Fluid

The average diff fluid changing interval is 50000 to 60000 miles. But that isn’t fixed. If the oil leaks or burns too much, smells bad or reaches too much lower level than required, you should check and change it.

Transmission Fluid 

The transmission fluid average changing interval is between 30000 to 100000 miles. That means it lasts longer than diff fluid. 

7. Oil Changing Cost

The oil changing cost is also different for diff fluid and transmission fluid. However, the oil changing cost is not much higher than repairing an engine. But you should have an idea about it. 

Differential Fluid

The two things (fluid price and labor charge) are important to determine diff fluid changing costs. The diff fluid may cost you approximately $30 to $80, and the labor charge may be around $40 to $70. That means diff fluid change costs between $70 to $150. 

Transmission Fluid 

An automobile garage may charge around $150 to $250 to change the automatic transmission fluid. Here, the $50-$70 is the fluid cost, and the $80 to $110 is the labor charge. 

Note: In both cases, the cost may vary as per your vehicle type, location, how much fluid your vehicle requires to fill up, etc. 

FAQs 

Is differential fluid the same as transmission fluid? 

The one-word answer is no, the differential fluid isn’t the same as transmission fluid. Significant differences between these two fluids include functional area, viscosity, temperature, pressure handling capacity, and many more things. 

Can you use transmission fluid for differential?

No, you can’t use transmission fluid for differential because the vehicle’s gear mechanism and transmission system have different requirements. However, they are named as fluid but formulated to serve different purposes. So it’s not recommended to use them interchangeably. 

What happens when differential fluid is low?

You can hear a cranking, grinding, or humming-like sound from the gearbox due to lower diff fluid. You may also notice gradual changes during cornering, accelerating, and decelerating. 

Final Words

So, now you have a good idea between differential fluid Vs. Transmission fluid. Both oils are formulated to perform individual work to ensure your engine’s smooth operation. 

The thumb rule of using motor oil is to check the user manual. From the manual, you’ll get a clear recommendation on which oil you should use for your vehicle and which not.