I Accidentally Put Transmission Fluid in Power Steering – Is It Bad?

Updated: | Author: Steve Freling | Affiliate links may be present.

Making sure to maintain the fluids in your vehicle is smart. You will ensure that the engine and other systems will continue functioning at their optimal level and probably prolong the vehicle’s life.

Regular maintenance is a great time to check and refill any fluids that need topping off. Some fluids, like power steering and automatic transmission fluid, can be mixed up as they are very similar in appearance and smell.

So is it bad if I put transmission fluid in my power steering reservoir?

It isn’t always recommended, but you can substitute transmission fluid for power steering fluid in an emergency, so it isn’t a total disaster. It might not be something you want to do every time you top off, though.

What is Power Steering Fluid?

Power steering fluid is a hydraulic fluid. It is pinkish, amber, or red and light or clear. It has a distinct smell described as the smell of burnt marshmallows. Your car will probably need power steering fluid unless you have electric power steering.

Different Types of Power Steering Fluid

There are two types of power steering fluid that cars currently use. One is a synthetic, and one is a mineral-oil-based fluid. They are similar but different.

Most modern vehicles use synthetic fluid specifically made to meet the needs of that car’s power steering system, while older models use the mineral oil type.

Why Does My Car Need Power Steering Fluid?

Power steering fluid is a hydraulic fluid that allows pressure to be applied to turn the wheels of a car. This fluid will make it easier to control and handle the vehicle, allowing for an easier and sometimes safer driving experience.

It is crucial to lubricate the moving parts within the power steering system. It will create a link between the steering wheel and the car’s drive wheels, and this is how it assists in turning the wheels of the vehicle.

Power steering fluid is also needed to keep foaming at bay and prevent corrosion in the steering gears and steering pump to ensure the best functioning of the system and to help prolong the car’s life.

How is Power Steering Fluid Different from Automatic Transmission Fluid?

Automatic transmission fluid is red and has a sickly sweet smell that differs from the burnt marshmallow smell of power steering fluid. It can also appear slightly more viscous.

Automatic transmission fluid is a hydraulic fluid, but it is heavier than power steering fluid and contains detergents and friction modifiers different from power steering fluid. Both will help with heat regulation but have different effects on friction.

It’s in the Friction

Power steering fluid is made to lubricate. It helps to reduce friction in the power steering system. Automatic transmission fluid has friction modifiers that make it almost sticky to increase the friction so that the gears in the transmission are guaranteed to catch.

Possible Problems if You Substitute ATF for PSF

If you substitute automatic transmission fluid for power steering fluid in the wrong vehicle, there can be issues. It may be okay for a short time, but doing so for a prolonged period will affect the seals and deteriorate the gearbox of the power steering system.

Determining If Substitution is Okay

Some say it is always okay to substitute, and they are both right when discussing certain vehicles. Cars manufactured before 1990 are usually able to handle this substitution.

Why? Well, this is because they are less sophisticated and aren’t engineered as precisely as more modern vehicles and probably don’t require the synthetic type of fluid. If this is the case, then mineral oil-based fluid will work in either system, and you can interchange the two.

When all else fails, read the owner’s manual, and the solution should be easy to determine. You always want to maintain the car as best you can to prolong the life of all the systems.

Should I Flush My Power Steering Fluid?

This is an interesting question. Most systems in a car that uses fluid will eventually need to be flushed. There are some exceptions as the technology used in vehicle manufacturing advances, but still, this idea is a safe bet for most car owners.

While power steering fluid does not have an expiration date, it will eventually wear down in the system, and a top-off may not do the trick to preserve its needed properties any longer. This is when you should consider a flush and replacement of fluid.

What Tells Me I Need a Flush?

When you need a flush, you will definitely know. As a person who regularly checks all the fluid levels in my car, I immediately noticed that my power steering fluid was getting too old to continue doing its job correctly.

How did I know? The fluid will be dark brown and is often also foamy in appearance, almost like some soap got into the reservoir. When you see this, flush the fluid and replace it. You never want to lose power steering while driving; it is a scary situation.

When All Else Fails

The bottom line is that if you don’t know enough about the power steering fluid, when to change or replace it, or if you can use automatic transmission fluid interchangeably, just take a peek at that owner’s manual, and all the questions should be answered.

I often forget this handy advice, but the owner’s manual is the key to many things. You can get all kinds of answers here, and it will tell you about the power steering fluid.

So my best advice is: when in doubt, check the owner’s Manual.

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About Steve Freling

Steve has worked for more than 20 years as an automotive mechanic, and later run his own repair shop for both cars and motorcycles. He's a maintenance freak, and generally pretty good at troubleshooting!

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