Can You Use Transmission Fluid for Brake Fluid? Get the Definitive Answer

When you’re in need of brake fluid and there’s none to be had, you might consider using transmission fluid as a replacement. It makes sense, as both fluids work towards keeping your vehicle’s brake system running smoothly. But before making the switch, it’s crucial to grasp the nuances between them so that you can make an informed decision on whether or not using transmission fluid in lieu of brake fluid is safe.

Can You Use Transmission Fluid for Brake Fluid? A Detailed Explanation

The short answer to this question is NO; you cannot use transmission fluid for brake fluid. Although both fluids are essential for your vehicle, they have different functions and properties.

Transmission fluid is designed explicitly for transmissions. It has different additives that serve various purposes such as preventing rust, cooling the transmission system, and lubricating gears and clutches.

On the other hand, brake fluid has a specific role- to transfer force from the master cylinder to your car’s brakes. Additionally, brake fluid has a high boiling point because its primary function is heat absorption.

Brake fluids are usually categorized into two types- DOT3 and DOT4. These two types have different boiling points, making them suitable for different vehicles depending on their use.

It’s important to note that using the wrong type of brake fluid can cause severe damage to your braking system and compromise your ability to stop your car safely.

What Happens When You Mix Brake Fluid with Transmission Fluid?

Mixing brake fluid with transmission fluid is highly discouraged since these two fluids are incompatible due to their different compositions.

When you mix them, transmission fluid can contaminate the entire braking system leading to a series of problems like:

Reduced Braking Power

One of the most significant problems caused by mixing brake fluid with transmission fluid is a loss of braking power. When contaminated with transmission fluid, the boiling point of brake fluid drops drastically. This means that when you use your brakes for an extended period or apply heavy pressure on them at once, the braking system will overheat quickly.

Experiencing overheating in your vehicle, which causes brake failure, may lead to a delayed stop. This can pose a substantial risk as it jeopardizes the safety of both yourself and fellow motorists.


Another issue associated with mixing brake fluids with transmission fluids is corrosion. Brake fluids are hygroscopic substances meaning they absorb moisture from their surroundings over time; this water causes mechanical parts within your braking system such as calipers and cylinders to corrode rapidly.

When mixed with transmission oil components like steel pipes contained inside hydraulic systems become exposed hence leading to accelerated oxidation due to low pH levels (acidity), acidity coming from glycols present in automatic transmissions fluids leading left unchecked can permanently dissolve metal surfaces especially those made using zinc alloys.

Seal Damage

Brake fluid is designed to work efficiently with rubber seals and hoses in your car’s braking system. When mixed with transmission fluids, it can cause severe damage to these components, leading to leaks. Leaks caused by seal damage in a car’s braking system can result in a loss of brake pressure.

This problem ultimately leads to increased stopping distance, making it difficult or impossible for you to slow down or stop adequately in the event of an emergency. It is essential that you have your brakes inspected regularly and avoid any mixing of brake fluid with transmission fluid as it could lead to severe safety hazards.

How to Identify if a Vehicle Has the Wrong Type of Brake Fluid

As previously stated, using the incorrect brake fluid can pose a significant danger to your safety, resulting in severe consequences. Therefore, if you suspect that your car contains the wrong type of brake fluid, it is crucial to examine it without delay.

Here are some of the signs that you may notice:

1. Reduced Braking Power

One noticeable sign is when your brakes start feeling spongy and take longer than usual to bring your car to a stop. This lag leads to weaker braking performance; in other words, its contact with high-boiling-point liquids becomes disturbed as it reaches near; stops reducing its efficiency.

2. Corroded Reservoir Caps

When moisture levels increase in contaminated brake fluids, they become corrosive due to contaminants reacting chemically with different metallic parts of the vehicle, causing container caps’ corrosion. Adequately sealing the brake fluid in a metal reservoir is crucial because incorrect fluid choice leads to disastrous consequences.

3. Changes in Color

Brake fluids reflect clarity when new, often transparent with a yellowish tint at times. As they age, they become slightly yellow or change their color to brownish hue altogether. Suppose you observe noticeable changes within a short period of changing your brake fluid (say within a month or two). In that case, it could mean that the system is contaminated.

What To Do if Accidentally Use Transmission Fluid for Brake Fluid

Using the wrong fluid in your vehicle can lead to various problems, and the situation becomes even more critical when it involves brake fluid. Vital to the braking system, using an unsuitable option like transmission fluid could result in disastrous consequences.

So what should you do if you accidentally use transmission fluid instead of brake fluid? Here’s a comprehensive guide on how to handle this situation.

Step 1: Act Fast

If you suspect that you’ve mistakenly used transmission fluid instead of brake fluid, don’t wait. It’s essential to act quickly and remove all existing brake fluids entirely before the damage becomes excessive. If left untouched, the effects of using the incorrect type of obstruction can worsen and cause greater damage or risk to driver safety.

Step 2: Check Your Car Manual

Every vehicle has its unique requirements concerning brake fluids. Therefore, it’s crucial to check your owner’s manual and see what type of brake fluid your car needs. The automaker will usually indicate everything you need from viscosity levels, boiling points, compatibility with specific types of engines or transmissions.

Knowing what kind of oil is best for your car will help you choose compatible brands which prevent contamination incidents from happening again in the future.

Step 3: Replace Your Brake Fluids Immediately

Once you know what kind of brake fluids are ideal for your car model, purchase high-quality products that meet or exceed manufacturer recommendations immediately. Using less expensive inferior brands can result in more multiple risks such as impurities found in tap water or even water mixed into cheaper brands’ formula; this often results in causing corrosion or other rusting issues that may lead to long-term damage.

We believe synthetic premium brands offer greater value than conventional oils because synthetic blends contain chemical compounds specifically designed for higher performance under harsh driving conditions – think driving on steep inclines during hot months; better performing brake coils don’t overheat as easily. It’s always best practice to exercise caution and use only certified oils.

Step 4: Clean Affected Parts Thoroughly and Inspect Them for Further Considerations

If you’re starting to see rust on your vehicle’s brake pads, calipers or brake lines, don’t ignore it. Corrosion is one of the signs that contaminated fluid is doing damage over time. To tackle the problem, clean the affected parts with a rust dissolver. Once you’ve got rid of the rust, inspect everything carefully for signs of further damage like leaks or other issues that may call for repairs or replacements.

When in Doubt, Seek Professional Help!

If you’re not sure what to do after finding out that you accidentally used transmission fluid for brake fluid in your vehicle, it’s best to leave these repairs and replacements to experienced professionals. They are equipped with the industry standards tools such as flushing equipment and utilize industry knowledge to determine what type of oil is suitable specifically for each car model.

What is The Best Brake Fluid for My Vehicle? 

Choosing the appropriate brake fluid for your car is crucial in ensuring impeccable brake performance and safety, and requires careful consideration of multiple factors.

Refer to Your Car Owner’s Manual

To select the right type of brake fluid, you should always refer to your car owner’s manual. Manufacturers recommend specific brands and viscosity ratings for each vehicle model depending on their unique requirements. The user manual provides clear instructions on what type of brake fluids work best for your car’s hydraulic braking system.

Two Types of DOT-Rated Brake Fluids

Brake fluids are classified according to their Department Of Transportation (DOT) rating. There are two types – DOT 3 and DOT 4. It’s good to note that using any other non-DOT-rated brake fluid is not recommended.

DOT 3 Brake Fluid

DOT 3 is one of the most common types of brake fluids available in the market. It has a boiling point of around 401 degrees Fahrenheit and is ideal for regular vehicles like minivans, trucks, and daily commuter cars with moderate driving conditions.

DOT 4 Brake Fluid

DOT 4 has a higher boiling point than DOT 3—about 446 degrees Fahrenheit, making it perfectly suitable for high-performance vehicles or those used primarily in racing events where extreme braking conditions may regularly occur.

However, it is important to be careful when considering using DOT 4 in regular passenger vehicles since they might not reach their boiling point during normal operating conditions. This could mean reduced braking power when compared to using DOT 3 fluids or even posing potential challenges for your brakes’ hydraulic system.

Factor In Temperature Range Requirements

If you live in an area with harsher climates or operate your car under intense heat levels -like most sports cars-, then you might consider a brake fluid with a higher boiling point to withstand the extreme temperatures. However, if you live in cool areas with milder climates, then sticking to brake fluids recommended for your category of car is ideal.

Synthetic Brake Fluids

There are two kinds of synthetic brake fluids – silicone and polyglycol ether (PAG). Synthetics operate differently when compared to their conventional counterparts. While silicone-based synthetic brake fluids last longer due to their moisture-resistant properties, PAG is less susceptible to moisture absorptions. Synthetics also demand specialized equipment and procedures to avoid oxidation issues during installation.

Always check before switching brake fluids!

Though manufacturers always recommend using specific types of brake fluids for each vehicle model in owner manuals, there are often variations among different car models and makes that require unique brands. Consult your mechanic -make sure they’re trustworthy- for the best advice on choosing the most fitting brake fluid for your type of car.


In conclusion, using transmission fluid for brake fluid is a concept that should be avoided at all costs. Although the two fluids may seem similar, they have different properties and should not be mixed under any circumstances. Additionally, regular brake fluid inspections are crucial in preventing oil contamination from happening.

Picking out the perfect brake fluid for your trusty ride can be a bit overwhelming, but don’t freak out just yet. The owner’s manual should be your go-to guide on this matter since it’ll have all the manufacturer’s recommendations.

You definitely don’t want to skip paying attention to this, folks, cause safety is super important when it comes to your sweet ride. Keep up with solid maintenance routines and make sure you drive safe no matter what!


Brake fluid

Automatic transmission fluid

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