Kohler will recommend 10w30 for a 25hp Command series. If that's what you choose, I'd want it to be Kohler branded 10w30 or any other 10w30 intended for small air cooled engines.
I ran Shell Rotella 15w40 or 5w40 in mine. IMO, heavy-duty, diesel, aircooled oils are where it's at for these types of engines.
Joel