Not to dispute what has already been said about oils, but my experience with my KDX 250 gives me a little insight into Glenbear's problem. The KDX 250, if it still has the stock jetting, is terribly rich, causing the familiar spooge and mosquito fogging. glenbear, I don't know what mods, if any, your bike has, but you can reduce the spooge considerably, and unlock a lot of hidden performance, if you will take the time to jet that bike correctly. The best thing you can do is to go to the next leaner slide, or, if you are mechanically capable, modify the existing slide. All of the carb circuits in that bike are way too rich, so take the time to jet it. I use Yamalube 2R at 32:1, and have almost no spooge from my bike.