OK Greg, don't buy that bike.
Just funnin ya a bit....that's not really what you wanted to hear, was it? It's actually a great looker and at $14,300 OTD, not that shabby a price. I don't know what TX sales tax would be but basing that price on TN sales tax, that would put the selling price at around $13,000 which is upper middle of the book ($11,900 to $14,500). If you can, wipe down the area you mention under the oil filter prior to your longer ride today. If it's still the same after your ride, that tells you it actually was filter residue.
I'm sure you've asked but with no history from the dealer, is there anyway you could speak with the previous owner? Not that you will always get good answers there but at least you can feel the previous owner out and may get a good idea of how it was treated.
Great bike for what you want to do with it plus some. Good luck in your decision and let us know how it goes.