I don't advise it with the red long life anti-freeze, but with the green stuff, dip your finger into the coolant and taste it with the tip of your tongue. It should taste sweet. Now you guys before you flame me for that routine I KNOW anti-freeze is poison but I have been doing that for 60 years and I am still here. It is not like cyanide. You don't need to drink it, ONLY taste it. Rinse your mouth out with wateer or whatever your favourite beverage is, spit that out and check the other one. Use a different finger for the other tractor. Another way is to put some in a clear glass container, then look at, it the greener it is the better concentration of A-freeze to water. The concentrated green anti-freeze (Prestone) looks like neon green right from the jug.