Most of the time it's an oil leak that covers the underside of the engine. To be sure, clean off the engine and over the net few days, look for the fresh leak. it's possible that the turbo is leaking oil but it normally ends up in the intercooler. It can leak out onto the outside but this is unusual, I don't think your car would run well at all if it was this bad.
It could be a leaky valve cover, CCV, or EGR leaking oil. It's probably not leaking inside so much that it's on the outside. I would think that the oil would dry out or burn off due to the heat though.
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