Wheel cleaner?

[Rocket Science Racing]

Thanks for all the quick replies, everyone!

I've been out there working on the car for most of the day. I've tried
straight Simple Green, some Prep-sol, even some brake cleaner. They are
pretty far gone, nothing even touched it. :-(

The exterior is going to need compounding. At least the engine bay and door
frames are gleaming! Back out to do the interior...

Thanks,

Scott