I use the west marine the green colored stuff, it’s over kill but I figured if all the water isn’t out at -120 even the diluted stuff is still strong enough?? I ordered it from Amazon right to the door. I winterize using a bilge pump off the ears an out of a 5 gallon bucket, fire her up let it run till solid color comes out the exhaust, shut her down done!!! Works for for the last 30 years✌️✌️