I have been using Caltex Havoline Formula 3 for aprox the last 30k, with 5k oil & filter changes. When i did the head gasket the other week i checked the bores, they where perfect, after 145k. The valve train was also near perfect.
Before that i used Shell Helix Plus for 20k, this is a 15w50 and is just as good an oil.
They are both Semi-Synthetic.