It looks like that thing lived on a red dirt road most of it's life.It's really not. It's on plastic and hoses on top of the engine. It baked in I think. there isn't evidence of oil leaks or grease. My 90 has a lot of oil leaks though. Mainly valve cover. It may be from the type of gravel they put on some roads. The dust hardens when wet. Crushed limestone maybe?