It might seem like you'll never be able to get rid of that oil stain on your pan, but there is a way to remove stains using vinegar. Mix a solution using two parts water and one part vinegar, and submerge your pans or utensils for a couple of minutes. After they're done soaking, you should be able to rub the stains away using a sponge and some water.
If, for some reason, the stain doesn't come off on the first go, then you can repeat the process and let the pan soak for a bit longer the next time.