I have 3 different brand of after run oil and ALL say they REPEL moisture not absorb, same as wd-40. While I have never stored an egine for more then 6 months I have never had an issue with wd-40 gumming up or attracting lots of crud. ALL oils will attract crud if crud is present which it should not be for long term storage. In my first post remember I said wd OR after run. I have no personal experience with ATF or ARO, I have actually never heard of ARO. All I meant to say is after run oil is fine but WD-40 will work also. Just remember I have never stored longer than 6months so wd could do what they say for longer periods of storage. One thing for sure is that ANY of these choices are better than not doing anything at all.