Review on Calibrated ITEQ Brake Fluid Tester Pen With 5 LED Indicators For Accurate Testing Of DOT3 And DOT4 Brake Fluids by Justin Buck

Theoretically, the tester is accurate and stable, this is very simple tool, it firstly invert 1.5V to 5VDC applied on the test pins, measure the resistance to compare preset values, when the resistance about 190K or above two LEDs will be lit, when the resistance below 190K, 3 LEDs will be lit, it means 3%, more lower resistance about 170K will turn on 4 LEDs.But brake fluid standard ( ISO 4925) does not have so called water percentage limit, so the seller said "calibrated for DOT3 DOT4 brake fluid" and when displaying 4% must change the fluid have no evidence. the test result is only for reference, we can't rely on the test result to decide should change the fluid or not.Moreover, the test is on the surface of the fluid reservoir, that point of moisture percentage is much higher than that near wheels, we know the fluid boiling point is much higher than water, when fluid getting high temperature, water was already evaporated.Conclusion: you can buy this tool to test your brake fluid for curious, doesn't make any other sense.