‎KINGBOLEN Brake Fluid Tester with 5 LED Indicators,DOT 3 DOT 4 DOT 5.1 Brake Fluid Liquid Tester Pen for Check Engine Automotive Accessories,Auto Brake Diagnostic Testing Tool Oil Moisture Analyzer

I used this on my 2017 Harley Davidson Ultra Limited to test the DOT 4 brake fluid in the brake master cylinder front and rear and also to check my clutch fluid reservoir.It seemed to work pretty well. I tested new fluid and it worked fine. I tested the oil fluid and it lit up across the board.I mixed new and oil fluid to test if this device will see any change and it did.I have not tested this product on DOT 3 brake fluid. The description for this product on Amazon says that it can test for DOT 3 and 4 but when you get the actual package it says only test DOT 4.One key note and I will put this in BOLD to drive a point, WHEN NOT IN USE, REMOVE THE BATTERY!The night prior to working on my motorcycle, I put in a brand new battery in this tester and tested to see if the lights will function and then I put it away. The next day when went to do the job, the battery was dead. I made sure that the device was off too. This thing will eat batteries so make sure you remove your battery in this device when you are not using it.

Fluids i know for sure are old and could be changed tests bad. New fluid in the bottle tests good. Only thing i know for sure is that it loves to eat batteries! I've started pulling the battery out when it's in the toolbox.

Tried it in my '98 Chevy Blazer master cylinder where I had a brake line busted and had to fix it and add new brake fluid. It tested 0 % moisture content. (expected) Then I tested the brake fluid in my '04 F-250 Super Duty. I knew it had an unacceptable amount of moisture content because last month I went to the store, had someone dart in front of me and my brake pedal went almost to the floor and felt hard. That happened one time only and haven't had it happen again. A fluke? The King Bolen brake fluid tester revealed more than 2 % moisture content. Guess what, I'm changing the brake fluid! There's too many chance driver's on the road for me to ignore my brake fluid. I need to be able to count on my brakes working every time. Thanks King Bolen!

Easy to use and need to provide your own battery though...no biggie but be forewarned... I wish they had a tool like this to check the viscosity and color of blinker fluid... That would be great.

It gives an accurate reading and works super well. But I find myself replacing the battery almost twice a week.

During a long hard trip, my clutch started to give out. No tension in the clutch handle. Read a few how to articles about boiling clutch fluid with to much moisture. Sure enough. I purchased this unit and it verified that fact before I spent any money on a repair. Checked brake fluid also, but no problem there. Great product for a small price.

Saw this on a YouTube motorcycle channel and immediately wanted one!Works as advertised. Very important on a motorcycle to have clean brake fluid and this definitely helps to achieve this. Just pull the cap off and dunk the 2 probes into the MC reservoir. Lights will light up from green to red depending how much water has been drawn into the fluid. EASY. Only thing that dropped a star is that you can't keep a battery(AAA)in the tester. I did and within 2 days it was dead. So I just take it out after every test...easy enough.

Just had my brake fluid changed at a Toyota dealer. Tried this tester out by inserting the entire metal probe into the fluid and it showed the fluid was contaminated and should be replaced. Tried again with only the very tips of the probes in the fluid and showed the fluid was good. Since there are no real directions with this and I get conflicting readings, I'm apt to say it does not work.