Hi there ..
I have changed oil every 6000 miles in my 93 since new and have about
163000 miles on the engine with no troubles at all...
I live in Canada and use a 15 40 weight in the summer and a 10 30 in the winter look in the owners manual or on the oil cap for the proper grade of oil.. it takes about 10 quarts with a filter change... good luck I know you will enjoy the truck