Do you need brake-fluid replacement?

I splurged on the $13 tester.

Wife has the Prius out of town just now so I can't take a reading but I'll see what it says next week.

 

I've learned that the ethanol in gas is also <> hygroscopic <>( has to look that one up).
There's a pretty simple test tube thingy to measure it too. To see it just put a few ounces of 10% ethanol gas in a glass jar and add a drop of water. You'll see the drop(s) of water at the bottom of the jar. Than if you swirl the jar around the ethanol absorbs the water and clouds up the gasoline. Eventually water separates out again. Good the test with some non ethanol gas too.

Thanks to everyone for sharing their brake fluid adventures, dealer service experiences and testing results.

 

The thing I like about this one is that it gives an actual number. It also comes with an insert that states an error range (+ or - 0.3%), a working temperature range (0-104 F), a storage temperature range, an altitude limit and a humidity limit. It makes me a little more confident that the product actually underwent some sort of testing. The number should make it easier to compare results over time. I don't know if the brake fluid in the lines would be worse than the fluid in the reservoir, so I plan to change when it gets anywhere remotely near 3%. So far, it seems to last about 7-8 years on my prii in Southern California (not right on the coast), assuming these testers are valid.