I only use 4:1 if the wheel is not really dirty, I simply use my degreaser on the rim as well (I normally use it on the tire and wheel well). Maybe I should diluting it to 10:1 and see how it does. It's just that I hate that stuff, it kill all my sprayers in no time. The only way I have managed to make them last is to remove the sprayer from the bottle after ever use and have it spray water to rinse it out. Really annoying and time wasting. I have tried several types of sprayers including chemical resistant ones and they all die within the first 3 use of the product. So make sure you rise out the sprayer or you will find this product is pretty costly to use if you have to spend 2$ or 3$ on a new sprayer with every use.
On the bright side, when used at 4:1 is cuts through baked in brake dust like there is no tomorrow. If your can't remove it all in the first go, spray a second time and it should remove the rest. As other have said, be very careful of fumes and sling with this thing. Hydrochloric acid is some of the nastiest stuff we detailers have to work with, a serious health hazard if you are not careful. So for me that means gloves. I don't use a mask. What I do is I hold my breath while spraying then I walk away about 5-10 feet before I start breathing again.