Are you sure its not just "extra" from the oil change? I get that almost every oil change, no matter how careful I am, and is caused by either what drained out, or the fact that I prefill my filters, and spill a little around the edge of the filter. It eventually stops. And, I've also noticed more often than not, the old gasket stays on the engine,and could easily be missed, doubling up, and causing a leak.