If you own a car or are enthusiastic about vehicles, you are probably familiar with power steering fluid and transmission fluid. At first glance, both of them seem to be quite similar.
Power steering fluid is not the same as transmission fluid. They are made for different purposes and have different properties. Power steering fluid makes it easier for you to turn the steering wheel, while transmission fluid lubricates transmission gears to make the shifting process smoother.
In this article, I will talk more about what separates power steering fluid from transmission fluid, whether they are interchangeable or not, and how often they need to be replaced.
Differences Between Power Steering Fluid and Transmission Fluid
To understand the key differences between power steering fluid and transmission fluid, let’s take a more detailed look at each of them.
Power Steering Fluid
Power steering fluid is a form of hydraulic fluid used in the power steering system. This system makes it so that less force is required to turn the steering wheel, especially while the car is at rest or traveling at low speeds.
If you’ve driven in an older car without a power steering system, you can probably tell the difference. It is very noticeable. Fortunately, almost all new vehicles use the power steering system.
The fluid’s role is to act as the hydraulic conduit through which the system can exert force on the two front tires to make turning them easier for the driver. The fluid also has the additional benefit of lubricating all the parts involved in the system, which allows them to function well and last longer.
In terms of physical appearance, power steering fluid is most commonly light red, orange, or pink. It may also be clear. It is recommended that you replace power steering fluid every five years or after 75,000 to 100,000 miles. For exact values, refer to manufacturer guidelines.
Transmission fluid is also a hydraulic fluid that serves the primary function of lubricating the vehicle’s gearbox. This allows gear transmissions to be carried out smoothly and efficiently, without any grinding between the internal components.
If transmission fluid is poor in terms of its quality, or if there isn’t enough of it, the gearbox can wear out over time due to friction, and gear transmissions can feel janky and rough.
Transmission fluids last a long time. Often, you don’t even have to worry about replacing them in your car’s lifespan unless you see signs of deterioration of the fluid or gearbox.
Transmission fluid can be divided into a few main categories:
Manual Transmission Fluid
As the name might suggest, this type of transmission fluid is used in most manual transmission systems that involve a clutch and gear for manual shifting. It is used in older vehicles; newer manual transmission vehicles are shifting towards the use of automatic transmission fluid for the additional benefits it provides.
It is thicker than automatic transmission fluids and comes in darker colors, such as brown. Most mechanics recommend that you replace manual transmission fluid every 30,000 to 60,000 miles.
Fun fact: Motor Oil can be used as manual transmission fluid. Even though it’s usually used to lubricate the engine, it has a somewhat similar set of properties to the ones required for manual transmission fluids.
Automatic Transmission Fluid (ATF)
Automatic transmission fluid is used in vehicles with an automatic transmission system. Besides providing the previously mentioned benefits of lubrication, this fluid also supports the automatic transmission system in carrying out gear shifts with the assistance of hydraulic pressure. It also acts as a coolant and ensures that temperatures don’t get too high.
It has a thinner consistency when compared to manual transmission fluid and has a slight reddish hue in terms of color. However, manufacturers have recently begun introducing their own colors, such as green and blue, to make their products stand out. It is recommended to replace ATF every 60,000 to 100,000 miles.
Synthetic Transmission Fluid
This form of transmission fluid is usually ATF created synthetically in a lab through chemical reactions. It is more effective in lubricating, breaks down slower, is less likely to oxidize, and provides users with numerous other benefits.
For further reading on the benefits of synthetic transmission fluids, refer to this article.
It can also be customized for specific vehicles. This category often offers the highest quality transmission fluid available.
For more information check our article about the Best Transmission Fluids and Additives.
Key Similarities and Differences
First, it is apparent that power steering fluid and transmission fluid are different for the most part. They have different properties, different roles, and different purposes. However, ATF, in particular, is a type of transmission fluid similar to power steering fluid.
Their similarity lies in the fact that both of these liquids are hydraulic liquids built to deliver pressure to a different area.
In fact, there are automatic transmission fluids that can be used as power steering fluids. Usually not the other way around, though.
Are Power Steering Fluid and Transmission Fluid Interchangeable?
The answer to this is not definite and varies on a case-by-case basis.
Power steering fluid and transmission fluid are occasionally interchangeable. Automatic transmission fluid, in particular, can be used as power steering fluid. However, power steering fluid cannot be used in the place of transmission fluid as it lacks the modifiers present in transmission fluids.
Using Automatic Transmission Fluid As Power Steering Fluid
Since both of these fluids are hydraulic fluids by nature, ATF can be used as a power steering fluid. It also has the added benefit of being able to remove dirt and grease from within the system.
However, this is not applicable to all vehicles safely. To find out whether you can use ATF in your power steering system, read the vehicle manual or consult an expert. In a bind, though, you can reliably use ATF; it will get the job done.
Using Power Steering Fluid As Transmission Fluid
Unfortunately, this is not a safe practice. Despite being able to serve the hydraulic purposes of ATF, power steering fluid lacks certain detergents and modifiers present in ATF.
These detergents are responsible for the removal of dirt and grease from the transmission system, a build-up of which can lead to inefficient operation or damage. The modifiers within ATF are responsible for controlling the amount of friction and, consequently, the heat generated within the gearbox.
However, surprisingly enough, you can use power steering fluid as your transmission fluid in a pinch (not if your vehicle requires manual transmission fluid, though!). It will take care of the hydraulics, but if used for the long term, it can cause damage to your gearbox, so be careful.
Mixing Power Steering Fluid and Transmission Fluid
It would be best if you did not mix power steering fluid and transmission fluid, as the difference in consistency and properties between the two types of liquids can cause inefficient operation in hydraulic systems. In worse cases, this can lead to complete failure of the hydraulic system – not something you want to risk.
You should only mix the same products (such as ATF with ATF) or products that are compatible with other products based on what the manufacturer states.
Power steering fluid and transmission fluid are not the same. Although they have a few things in common, they are designed for different purposes and have distinct features. They generally cannot be interchanged without negative consequences, but if you’re in a pinch, you can use ATF in place of power steering fluid and vice versa.
Using ATF as power steering fluid is usually safe (check your vehicle manual for confirmation). However, power steering fluid should only be used in place of ATF in an emergency as long-term use can damage components within the gearbox.