Let the real experts tell you more, but, between fresh dino and syn at 5,000 will depend on the particular car somewhat=do UOA to check.
Odds are the synthetics, well, at least the real ones will be in pretty good shape at 5,000.
Mobil 1 definitely doesn't burn particularly quickly in all, or even most engines. Unless you're talking about Germany or Belgian Castrol (0W30 or 5W40), Syntec is a rather over priced Group III oil...that is, Castrol can't label it as synthetic in Europe, but they can get away with it here. Not that Syntec is bad, it is more that it is overpriced. Espicially since Mobil 1 in 5 qt jugs is cheaper in most Wal-Marts. Amsoil certainly makes some great oil, but you can't really buy it locally over the counter, and their oils are only economical on longer drains.
I can't make a recomendation between 5w30 and 10w30 in that application, but someone else probably can. Otherwise, what does the manual say? What does the manual say in European/Australian cars? If I had to make a vast generalization, I would guess that GC or Mobil 1 10W30 would do well.