Leaking oil/water out the tailpipe

[Treyw147]

2011 Subaru sti limited

So I just changed my oil, but not the oil filter due to not having the correct filter wrench. I do plan on changing the filter today, so dont worry. But after changing the oil, i decided to let the car run. cycle all the new oil and such. about 20 min later i hear a funny noise. the tail pipe was shaking and making a deep rattling sound as if it was trying to spit something up. then i notice that fluid was dripping out at a slowly. After further investigation, it looked like oil with water mixed together. I didnt have this problem at all before i changed my oil. Whats going on?

 

[HolyCrapItsFast]

It could be carbon mixed in with the water. If it was idling for 20 minutes it is conceivable to accumulate a significant amount of water in the muffler. Any carbon deposited can mix in with it and it would look like oil.

What does it feel like? If it is oil it should feel oily. One thing you can do is take a sample and put it on a clean dish and place it in the oven at it's lowest setting for about 15-20 minutes. That will allow the water to evaporate and and reveal the substance to be either oil or carbon.