So this is the scenario you discovered that your car has a low power steering fluid level. You’re in the middle of the road and found a bottle of brake fluid in your compartment. Then you asked yourself, “Can I use brake fluid for power steering fluid?” In this article, we will find out if this is possible and what the risks are if we do.
Brake fluid and power steering fluid are hydraulic fluids but with different purposes. They are not interchangeable and should not be used interchangeably. Let’s dive into the details.
Can I use brake fluid instead of power steering fluid?
The answer is no! Brake fluid is made up of different chemicals than power steering fluid and will corrode your system if you use it instead. Brake fluid is alcohol-based and can cause damage to your power steering pump, seals, and O-rings. If you use it instead of power steering fluid, the alcohol will start to eat away at these parts, causing leaks and failure.
Power steering fluid is made to lubricate and cool the system, while brake fluid will only corrode your power steering pump. This will cause it to fail over time. You should never use brake fluid instead of power steering fluid because it can damage your vehicle’s components.
Reasons why you can’t use brake fluid for power steering
To better understand why using brake fluid instead of power steering fluid is terrible, it’s essential to know the difference between the two types of liquids.
Brake fluid and power steering fluid are two fluids that you will often see in your vehicle. Both of these fluids are used in a hydraulic system, which is a system that uses liquid pressure to move parts.
The most apparent difference between brake fluid and power steering fluid is their composition and purpose.
Different chemical composition
Conventional brake fluids are DOT-3 type containing glycol ether, DOT-4 type, and DOT-5-1 containing 30-50 wt. % of a boric acid ester and glycol ether.
Brake fluid is ether alcohol-based, which means it has a high boiling point. To visualize this, water boils at 100 degrees celsius, whereas brake fluid with a high boiling point will boil around 300 degrees Celcius. It also has a low viscosity, which flows easily through the lines and hoses.
The power steering fluid comprises at least 92 percent of a mineral lubricating oil and 0.5 to weight percent of an oil-soluble estolide of a hydroxystearic acid.
In contrast, power steering fluid is petroleum based and has a lower boiling point than brake fluid. The fluid is used to power the steering mechanism, allowing you to move your car easily. It has a higher viscosity than brake fluid and is either mineral-oil or synthetic oil blended with additives.
Related: Can You Mix Fully Synthetic With Semi Synthetic Oil?
Different purpose
Another reason you can’t use brake fluid for power steering is that they serve different purposes for different vehicle parts.
The primary purpose of brake fluid is to transfer force into pressure in the brake system. This is done by compressing the fluid in your brake lines. The pressure in your lines depends on how much force you apply to them (like when you press down on your brakes).
The heat in the brake’s hydraulic system will eventually lead to moisture condensing. To prevent damage, brake fluid absorbs the moisture.
On the other hand, The main purpose of the power steering fluid is to lubricate the power steering pump. The power steering pump creates pressure by directing oil through very small passages inside it — these passages need lubrication so they don’t wear out prematurely.
Power steering fluid also keeps all these moving parts clean to operate smoothly and efficiently.
What can I use instead of power steering fluid?
If you’re running low on power steering fluid, you can use automatic transmission fluid or ATF as a substitute. Both are hydraulic fluids, so they should be able to lubricate the power steering pump and keep it running smoothly. They consist of:
- 85-90% base oil
- 10-15% additives
These additives are friction modifiers and detergents to clean out dirt and grease from the transmission. These additives may cause problems with the power steering system, so it’s best to use ATF only when you have no other choice.
Conclusion
Never use brake fluid, or any other kind of brake fluid, for power steering fluid. They have different formulations that aren’t compatible with each other. When you have to choose a substitute for power steering fluid, automatic transmission fluid is a better option than brake fluid.
However, these additives have downsides, as they may damage your power steering system.
