Newer engines, up to 200,000km I would run a good quality 10W-40. Above 200,000 I would consider running a 15W-40. As for brands, I would recommend either Penrite or Nulon. Before oil changes make sure you run an oil flush like http://www.nulon.com.au/products/Engine_Treatments/Engine_Oil_Flush/. The 5S is fairly prone to sludge so it a good idea to give it a flush.