Brake Fluid Tester Pen with 5 LED Indicators, Universal Car Accessories

It seems to work well, tried it various times, and no difference in outcome. Aside from the battery door (Battery not included, just a heads up) being a bit of a task to remove, it's a good little tool.

Does the job and good price

This is fast and easy to use. Display is bright. Performance and quality in terms of accuracy is hard to measure. It can definitely tell the difference between brand new fluid and water. Those results were exactly as your expect. On my used fluid, the results ranged from 2-4% and I took several tests to conclude the mode reading of 3% was probably fairly accurate. For the price it's a reasonable value even if not professional quality. Battery required is a single AAA, and the re-closable bag is a good place to store both between uses.

I was highly skeptical that I needed one of these in my life. Then I opened up my brake fluid which was supposedly being done at the dealership for the last 3 years and it was green. No not black, green. Yes that's right, the brake fluid was green. I'm talking green like Green Eggs and Ham , yes Sam I am. I threw the test pen into the master cylinder and it said 4%, which I guess is red for dead. This is the easiest thing to use in the world, you click the button unscrew the master cylinder throw the tester into the brake fluid and look for the light. You have a 5 position light that indicates what percent the amount of water in the brake fluid is. Green for go, yellow for warning and red for dead. Looking at the brake fluid you could clearly tell it was very bad so obviously the tester itself is accurate. The build quality seem sufficient for what it is, it does not say it is waterproof so make sure to only immerse the testing probes. I recommend not storing a battery in the pen if you're going to not check anything long term. Oh yeah you need 1 AAA battery that should last forever. Now I'm spending $200 on Amazon for an automatic brake flushing machine so I never have to pay the dealership again. You should too, It'll help the economy.

For good maintenance, I like to follow car manufacturer's recommendations. It was time to flush out OEM brake fluid on my Toyota Tacoma. Used this sensor to see if old fluid was contaminated. It showed a small, minor amount of water contamination. This was good to know. The sensor was easy to use and worked perfectly.

Told me what I needed to know (fluid OK in a used car I just got). Seems reasonably accurate, tested on some new fluid I had then added some water to a sample (2% then 3% by weight) and this measured it correctly.

Excellent

I couldn't tell you if it worked or not. I tested several vehicle and all of them were older than 10 years and it gave same reading on everyone. Is it defective? I'm unsure. Would I purchase again? Probably not. Is it worth the price? I would say yes. If it detects high moisture in one vehicle, it paid for itself many times