I am getting ready to flush the antifreeze in my truck but have a few questions. I found the fleetguard es compleat propylene glycol but didn't know if this is what I should use or not. Also, what is the best way of testing the strength of this new antrifreeze? I have a hyrdometer but noticed it says for ethylene glycol and figured it wouldn't work on this new propylene stuff. Do they make a special hydrometer for propylene and where would I find one?