:deadhorse The proper way is to fill them enough so that the fluid level is higher than the top of the wheel, so that the wheel itself is never exposed to air.This is how you can have tire/wheel assembly's full of calcium chloride for years and not have the wheel rust out.Not to the top of the tire, but over the top of the wheel.Of course, there are those out there who have never done it, probably never seen it done, but can tell us exactly how it's supposed to be.Now, you can put a single gallon, 50 gallons,25%,50%,whatever you or whoever is doing it wants to put in there, and it'll "work". Regardless, if the wheel is exposed to calcium chloride and air, IT WILL RUST OUT!!FAST!!!! :deadhorse :stirthepot:avid