Rotax Rick (whom I bought my 582 from) puts straight 30wt in rotary valve and that is what I have been using as well. I would NOT run it dry and expect premix to do the lubricating (I also premix). My understanding is the rotary valve shaft is a seperate and completely sealed unit from the crank case/ pistons etc that gets lubed by the fuel mixture. I doubt it truly matters since it is just supposed to be recirculated anyway.