Why is oil leaking into my coolant resevoir

Blowed head gasket or intake,has car ran hot?

Ditto. How does the oil look?

If ur getting oil in it ur probably getting coolant in ur oil. Could seize ur motor. Like they said bad gaskets.

Well I have had this happen to my 91 Mitsubishi. When I tore down the engine and pulled the heads off, I noticed each piston chamber has and water jacket and oil ports that run near the cylinder. Now what happens is either you over heated the engine to redline, and or low oil in crank case. These walls that separate from the two chambers are very close so if it got hot or low oil it could cause it to crack and as a result leak oil, burn oil, leak water into the piston head! If your case oil in the water , Check the oil on the dipstick. If it looks good black like oil should there is no problems there. But if it looks milky or did colored you deffinately have antifreeze leaking into your oil! And that's not good. Hope this helps, I'm no mechs but I experienced a lot of technical difficulties over various makes and models lol