Mobile 1 full synthetic 10w30 for summer and 5w30 for winter. Well thats how I change my oil every season. You don't have to go with full synthetic and just with conventional oil, I don't feel any difference, just safer in the long run I guess. I've tried Royal Purple, Castrol Full Syn. Use the dealer oil filter.
I've read though that to truly get "full synthetic" it should say Made in Germany on the Mobile 1 bottle. I just try to get whatever is at my local Walmart.