I was just recently doing some minor inspections of things on the car and noticed when you rev it to about 2-3K, that's all I do in nuetral anyways, I get this black dusty looking crap from the tailpipe. Well, it seems to dusty but when I wipe it off my hands it's more like an oil. So my qeustion is, is this o.k. or do I need to worry about this?