If your archenemy remarks on your oleaginous skin, she's not giving you a compliment. She's calling you oily-faced.
You can impress your friends by commenting on how disgustingly oleaginous your pizza is, or despair over the oleaginous state of an ocean bay after an oil spill. Either way, you're using a fancy word for greasy or oily. And if you run into a particularly slick car salesman, you can describe him as oleaginous too. The adjective oleaginous comes from the Latin root oleaginus, "of the olive."