Not sure if any of you have used a refractometer. Wholesale Parts and Tools.com has a metal-bodied, model RHA-100ATC on sale for 34.95, plus shipping. I've seen them go for twice that amount. These are a bit more reliable than the cutesy little colored ball, specific gravity jobbies you get at Wal Mart. A good tool for the box.
Just passing along....

 

(A refractometer is what you use to measure your coolant and/or battery acid. There's an interesting connection between the electrolytes in your anti-freeze/coolant and bad grounding to your chassis; especially in cars and trucks. A bad ground can ruin your coolant, which then ruins other related things...) It's more than just a simple boil/freeze point tester.

 

Yes, the following link is directed at diesel engines, but the information is something to generally keep in mind.
http://www.buyerzone.com/constructio...e-coolant.html
I'll shut up now.