If it won't wipe off with a dry shop rag, Barkeepers Friend will make it shine like new. It's non abrasive so it won't scratch. Make sure your cloth is clean so it won't scratch. The more black smutz there is indicates how much fun you just had.
It usually isn't in the exhaust, but on particularly hot days when I'm exercising the engine, I'll still weep some Cosmoline from places in the engine bay. It's a waxy coating that is applied to prevent rust during shipping / storage. It starts out yellow/tan but gets sticky and dust/dirt adheres and it turns black/brown pretty quick and will start to seep when it gets hot.
Like x 1
