The same thing happened to me when I tried to mix the oil with the fuel. I tipped in the oil slowly and you could clearly see all the blobs of oil in the fuel. It was like oil-meeting-water. You could see the blobs. So i shook up the bottle very fast and hard and got it fully mixed in. I have left my fuel for a few weeks now with the 2 stroke oil still mixed with it, and to my suprise it hasnt seperated!

I thought over time, it would seperate, but I couldnt see any such thing. But of course, before I used it again, I did shake it up abit more, just to mix things up again. Works like a treat.