I've done a lot of searching and found this thread of the same problem however, I'm reluctant to do this due to risks. Has anyone had this problem and found a better/safer alternative? http://forums.nasioc.com/forums/showthread.php?t=929586
Meg's has a professional lineup of wheel acid that will clean this off in a jiff. I have some and use it on rare occasions where I just can't get it off with normal products.
Zep heavy duty engine degreaser works perfectly, if used properly. Dilute it a bit, spray on, wait 3-5 minutes and clean well.
some old school carnauba wax which is a pain in the ass to work in but will take the heat and last for a month is the best preventive