tested this tool on the cold tab water. Measured density of water from the same glass four times and got four wildly different measurements. My best guess, you are on mercy of friction force between the red float and clear plastic housing that supports it. In a good run you get accurate reading. But most likely you getting a total garbage reading. It is a shame to see a great quality resin and plastic parts been wasted. More waist goes to the dump. :(

Water amp; Antifreeze had the same reading amp; it was all the way to the top of Protection, i guess i wasted money on Antifreeze since water had the same reading..!! Junk....

I used it on 2 different vehicles it had some residue inside cleaned it out the arrow went all the way to the top on both vehicles and then I used water Same result it's garbage buy the (Peak) one it works as it should

Realice una prueba con un refrigerante ACDelco y no da los valores de congelamiento, ni ebullicin suministrados por ese fabricante, tambin lo compare con un refractmetro y nunca se igual la prueba del dispositivo.

Don't waste your money on this one despite the fact it bears the name of a company that knows a thing or two about antifreeze..... this tester is pure crap. After following the advise of others i. e. filling it slowly to avoid bubbles and doing a lot of "tapping" while holding it perfectly vertical, its pointer gave a maximum indication while testing premix 50/50. I bought another tester that uses floating balls and tested the same 50/50 solution. It gave expected results so I'm trashing the Prestone.

It did not function due to cracks in the rubber Bulb.