Originally Posted by CdnoilRAM
I've never had a shiny frame, mine have always been matte black. That said, Simple Green is my go to cleaner for everything on my truck, especially the engine bay. Interesting to know though.
I've had lots of simple green on my paint before, it won't affect the clear coat at all. The underside doesn't have a clear coat to protect the top layer of paint, so this may account for why it dulled down after cleaning.
Good to know. I use it for non-truck purposes. That makes sense about the clear-coat. AND, Cd.... we all think you have a shiny frame!