Sounds like Cosmoline. Typically, imported cars are treated with it for the long boat ride to prevent damage to the unpainted/uncoated items under the hood. Once completely dried (cured) it is hell to remove, so I'd get it off now. I've never seen it on a domestic car though, so I have no idea how it got on yours. My GT didn't have a trace.
I bought a new Nissan a few years back that was driven straight from the port to the dealership, at my request. By the time it got to the dealer (a couple days later), the Cosmoline was cemented to the engine compartment and I was never able to remove all of it.
BTW, that Nissan was, by far, the worst vehicle I've ever owned. It had problems in every area (paint, transmission, engine, electrical, interior trim) and it was completely worn out by 90,000 miles. This was with the wife driving it and good maintenance. I've had Ford, GM, Dodge, and Fiat, but Nissan is the only car brand I will NEVER buy again.
Owner1