So I've never given antifreeze much thought. Our cars are newer and were routinely serviced (including checking and filling all fluids) by the dealership service dept. But with the mustang, the boy and I are trying to do as much as we can on our own. I picked up an antifreeze tester with 6 floats...1 is good, 2 is gooder, 3 is gooderer, and so on up to 5. It it floats six floats, it says "unsafe". Well, we tested ours last night, and it floated 6 floats. It's clear and bright yellow-green, so no need to change it I reckon. So whats the fix...just suck some of it out, and add water until it floats just the 5 floats?