5-30 is what the factory calls for. I would also fill w/clean oil and use STP engine flush drain & re-fill just to clean out the engine. you could also use trani fluid 3 qts +1 of oil for 20 min and drain & re-fill. and yes I have done this w/several vehicles.
with higher mileage vehicles, parts are starting to get worn, i would reccomend a heavier weight oil. 10-30 in warm climates like so cal, and durng summer, during winter i would reccomend going to a heavier oil. if temps regularly get below freezing id go with 20-50, i am currently running castrol 10-40 synthetic and am very happy with it. whatever you do stay away from 5-30! especially in a vehicle with 160k