I am running Wildcat 30% and I have NEVER ran the engine dry after flying. Lately I have been only flying twice a week, and none of my engine have show signs of any rust. They are stored outside in my pole barn, not heated or climate controled in any way. The only thing I do is drain the tanks. The only time I use any kind of after run oil is before the winter, and then I run the engine dry and load it up with the oil for long term (4-5 months) storage.