I am sure your oil filter stand gasket is leaking, and then the oil is getting onto this joint. Or you might have a leak somewhere else. How much oil are you using/losing? You should probally replace the oil filter stand gasket if it is leaking. I just replaced mine the other day, and it you can do it in a afternoon. Just make sure to replace all the gaskets. I think it cost me less than $5 for the gaskets. Oh, and be careful with the oil cooler lines. Here is the link on how to do it: Oil leaks fixed!