Just my 2 cents!!
I have had a lot of PM's from some people who are a whole lot smarter than me on this subject. The general consensus is Castro syntec 10W40 for almost all climates. That was after about two weeks of painstaking research. Most experts recommend oil changes of no more than 7500 miles or once a year. Now this depends on your driving habits and if you track it. I don't, but if you do, then you should change more often. Check out the this thread.
http://www.987forum.com/forums/showthread.php?t=21477
yes this subject has been beatin to death, but I empathize with anybody that is still confused as the experts will not come out and officially endorse an oil!!