I have a 1993 OMC Cobra and have yearly changed the stern drive oil since 1993. As long as I can remember it comes out a dark colored brown and is pretty stinky. This year was no different. However, I have been reading about the milky look to the oil & I think this may be it. The outdrive has alway performed well & it gets used a lot. Do I need to worry about this or is it fairly common. <br />Also, in the past few years I have been using a generic brand of gear oil (80W90) that I get at Autozone. Is there a difference between this and marine grade gear oil?<br /><br />Thanks for your input.