Well, I have Sirio, OS, SH, and Picco engines. I thought most engines had silicone gaskets, but maybe it's some other material. I still use ARO, but only for long term storage.
I have yet to notice any leaks or problems with any of my 7 different engines, but Woodie you're making me nervous. I guess I'll get another bottle of the ARO and forget the WD-40.
To be honest, I prefer to idle my engines dry by pinching the line or flipping the trucks upside down, then restart them until they won't fire anymore. If it's only gonna be a couple days, I skip the wd and oil all together.