If you own a vehicle, how fast it gets you from one place to another is important but that is just half of the story. It is also important to pay attention if your car has enough stopping power to stop your vehicle if it needs to. Here we will talk about your car’s braking system and consequently the brake fluid.

The brake fluid is a special fluid that applies enough force to the brake calipers to decelerate a moving vehicle. This fluid is compressed hundreds of thousands of times in its lifetime and its quality may deteriorate over time.

7 of the best brake fluid testers available now

1. MR CARTOOL DY23 Automotive Brake Fluid

Stand out features If making your vehicle safe for your family and saving some money in the process is your goal, the MR CARTOOL brake fluid tester may just be the tester you are looking for. This is a true all-in-one brake fluid tester as it works with DOT 3, DOT 4, and DOT 5 brake fluids. This eliminates buying another one if you have a different vehicle that uses another kind of brake fluid. The tester is in a handy handheld gadget size with a gooseneck probe which makes it less prone to dropping. The LED indicators are bright and easy to see even in brightly lit areas. Made with a durable ABS plastic that is resistant to bumps and nicks, with a durable gooseneck detector that is resistant to corrosion. MR CARTOOL Automotive Brake Fluid Tester: image
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2. OBDRESOURCE BF-200 Brake Fluid Tester

Stand out features This handy gooseneck configuration brake fluid tester incorporates a large and high-resolution LCD screen that is backlit for easy visibility. The display is clearly visible even in broad daylight or bright and harsh shop lights making this very handy in any lighting condition. The probe itself has led lights that let you see the fluid and if there are any particles floating around the reservoir. While battery-powered, it also has an automatic shutdown feature that shuts off the power after 5 minutes of inactivity. This is definitely a must-have device for any car owner. Auto Diagnostic Testing Tool BF-200: image
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3. OEMTOOLS 25269

Stand out features Nothing beats the portability and ease of use of a pen-type brake fluid tester and the value of being able to use it with just one hand. Prevent brake system failure by using this handy and portable brake fluid tester. Built-in led light on the tip of the probe itself ensures high visibility when inserting it into the reservoir. In addition, get the most out of its battery life with its auto switch-off function when not in use. As if that is not enough, this tester is compatible with all brake fluid types for the ultimate convenience. OEMTOOLS 25269 Brake Fluid Tester: image
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4. OTC Tools 4598 Brake Fluid Tester

Stand out features This tiny but highly useful fluid tester pen is just about the size of a marker pen. Specifically tested for use with DOT 3 brake fluid formulation, this tester is extremely useful in the common driver's garage. It is quite easy to operate even with one hand, freeing you up for other tasks. The no-fuss LED indicator lights show you exactly if your brake fluid needs replacement just by their colors. OTC Tools 4598: image
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5. MR CARTOOL DY23-B Brake Fluid Diagnostic Tool

Stand out features The MR. CARTOOL DY23-B is the big brother of the DY-23 and the difference lies in the Dy-23-B having a large LCD screen display which makes it easier to read and use. They have the same features in terms of universal compatibility across all kinds of brake fluid types. The chromed probes are resistant to rust and any form of corrosion, prolonging the longevity of the device. The 250 mm gooseneck probe also has a LED bulb on the tip for high visibility when you insert it into the reservoir. MR CARTOOL DY23-B Brake Fluid Diagnostic Detector: image
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6. OBDRESOURCE BF-100 Brake Fluid Tester

Stand out features This nifty brake fluid tester combines the form factor of the pen testers with a gooseneck probe, allowing you to have the best of both worlds. It has the slim profile of a pen tester with a gooseneck probe attachment, allowing ease of use even in limited spaces. Its rugged non-slip design prevents any accidental drops from happening as well as comfortable to hold and grip while working. The tester works on all types of brake fluids, from DOT 3, DOT 4, to DOT 5 which makes it a universal option, truly a bang for the buck addition to your toolbox. OBDRESOURCE BF-100: image
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7. Allsun Portable Brake Fluid Tester

Stand out features The Allsun brake fluid pen tester retains the convenient and easy-to-use pen shape with the distinction of having a slender and elongated tip that houses the probes. This modification allows the one-handed operation of the tester. The operation buttons are conveniently located in an accessible place as you point the probe inside the brake fluid reservoir. The pen is powered by 3 pieces of 1.5V button cells. Battery life is always optimal as it shuts down automatically while not in use. Allsun Portable Brake Fluid Tester: image
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Top Pick
MR CARTOOL DY23 Automotive Brake Fluid
This is where the brake fluid moisture tester comes in as its primary job is to make sure that the brake fluid still retains its properties to be effective. There is a ton of products claiming to be the best out there, and at best may cause confusion. We do not want that to happen so we came up with a list of 7 of the best brake fluid moisture testers available for you to purchase. We start this list with our own top pick, the MR CARTOOL Goose Neck Brake Fluid Tester, with its extremely user-friendly features. This tool is ultimately better than your run-of-the-mill brake fluid test strips, as you can use it indefinitely on DOT 3.4, and 5.1!

Using a brake fluid tester

Before we tell you anything about how brake fluid testing is done, let it be known that brake fluids lose their effectiveness over time. The fluid can take on moisture and lose its compression properties, which is quite important in a braking system. Too much moisture in the brake fluid can cause lines to corrode and can cause accidents in the long run. Using a brake fluid tester used to be cumbersome and expensive, but now technology has made it easy and quite straightforward. A brake fluid tester is usually a handheld device that contains LEDs, and a guide or legend that tells you what condition your brake fluid is. Testing with either an electronic brake fluid tester or a brake fluid tester pen can take anywhere from 2-5 minutes tops if you know what you are doing. The first thing you need to do is make sure to be very careful when dealing with brake fluid, as they are corrosive and can damage your paint. Always keep a rag or cloth nearby to wipe off any excess fluids that splash onto the surrounding areas. Wear eye protection and gloves if at all possible. Make sure that the tester you are using is compatible with the brake fluid you are using, and when that is done, remove the caps and dip the probes into the fluid. Take a close look into the display of the brake fluid checker and the reading should be anywhere from 0-4%. If by any chance you see a 4, that is an indicator that you need to change your brake fluid. Remove the probes, wipe them off and then close the reservoir as quickly as possible to avoid contaminants from getting in. As far as usage is concerned, that is how to test brake fluid, easy and fast. However, the hard part is making sure that the tester you are using is the correct one. This brings us to the next part, which is a handy guide for you when choosing one for your car.

Brake fluid tester buyer's guide

Choosing from among the almost limitless number of products on the internet can be a bit of a challenge, and the checklist below will prove to be quite useful in narrowing down your selection.

Types of Brake Fluid

Brake fluids come in different kinds, there’s a standard on which the fluids are tested on and it is the DOT that stands before their number. This simply stands for the Department of Transport and they set the safety regulations that make the fluid safely and performing within an acceptable performance. Right now we use DOT 3, dot 4 brake fluid, and DOT 5 their differences lie in their boiling points with the lowest starting with DOT 3 with the highest one in DOT 5. Before you even think of the tester, focus on what kind of brake fluid you have on your car. There are different formulations and brands, and each of them will have a different level of moisture absorption. With this in mind, check brake fluid tester reviews and get the one that is compatible with all types of brake fluids.

Specific Features and Other Accessories

In general, brake fluid testers work by measuring the moisture level found in brake fluids, the old ones use brake fluid test strips autozone and the more modern ones will make use of LEDs or LCD screens that display the information you need. Some may come with extras, such as batteries or carrying cases. Others may have extra durable armor or casing as the probes are quite sensitive. Depending on what you need or what you can live without, consider these when doing your selection.

Build Quality

This one should be a no-brainer, but you do have to be mindful of one thing, brake fluid testers have extra sensitive probes so make sure that the one you are buying has ample protection for this part. Look for one that has a tough outer casing, preferably with a rubbery material that will cushion the instrument against the accidental bump or the occasional drops. Remember that this device will probably be living in your toolbox, so extra protection is definitely needed.


With these devices, having a higher price does not necessarily mean that it is of better quality. However, having a higher price is also an indication that higher quality materials are used, as well as proper research. There is always that balance between price and what it can offer, so look at the features that come with the brake fluid tester. When deciding if the device is worth it, tally the features with a similarly priced device, and then whoever has the most features win.

Frequently Asked Questions (FAQs):

What Is Better DOT 3 or DOT 4?

The DOT specification is an indication of how high that particular brake fluids’ boiling point is. DOT 3 has a lower boiling point than a DOT 4 brake fluid. This does not mean that DOT 4 is automatically better though as it is entirely dependent on what your car’s braking system specifies. Those with higher boiling points are well suited for high-performance racing cars, as their braking systems tend to generate enormous amounts of heat. Then you also have to consider that the DOT 3 brake fluid tends to absorb less moisture over time, so that makes it the lower maintenance and economical choice.

What Does a Brake Fluid Tester Do?

Brake fluid is a hygroscopic fluid, which means that it naturally attracts moisture from its surroundings. When the moisture reaches a certain level, it loses its compression qualities and may be dangerous to use.

The moisture content is what brake fluid testers are made for because they measure the level of moisture found in the brake fluid. They usually measure the moisture content via probes that get inserted into the brake fluid reservoir and give out readings in seconds. The readings are usually LED lights or via an easy-to-read LCD screen. The readings are what determines if the brake fluid can still be used or is due for replacement.

Also you can watch this video from YouTube:


What Happens If You Put Antifreeze In Your Brake Fluid?

Not only does this not make any sense at all but is downright dangerous. Brake fluid is already corrosive on its own, but adding in antifreeze may damage your braking system and its expensive components. Besides the fact that it is not really that expensive to change out your brake fluid, but messing around with something as crucial as the barking system of a vehicle you ride on is just not practical. Furthermore, the vehicle will recognize it and the dashboard indicator light for brakes may light up, telling you that there is something wrong with the brakes. A word of advice, never DIY something with the braking system of your car.

Does Brake Fluid Mix With Water?

Yes, brake fluid will mix with moisture if allowed to do so. Brake fluid attracts moisture from around it by nature and it is strongly advised to ensure that the reservoir remains airtight at all times. Moisture is the whole point of having a brake fluid tester and that it should be ensured that only the most minimum should be in the fluid itself. Ideally, any moisture content that is above 2% warrants that the fluid should be replaced immediately. Moisture in the fluid can cause internal parts of the braking system to corrode and thus make the vehicle unsafe to use.

In conclusion

Prevention is always better than cure and it is most especially true with vehicles. Not only will it potentially save your life, but it will result in savings in the long run. Simply following your vehicle’s instruction manual, especially in replacing various fluids in your car, is enough to keep you out of trouble. However, just to be sure specialized equipment like the battery fluid tester is always a plus to have. The gist is getting moisture into brake fluid is a bad thing for the vehicle and its occupants. Moisture can corrode metal or metallic parts in your braking system. Rust particles are a real danger as they can clog up the hoses that make the calipers work and apply pressure on the brakes when needed.
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