I was told once that as long as the oil rating on the can was the same as the owners man. called for you'd be alright.

I had a 89' buick lesabre w/the 3800 engine and
I bought it with 172,000 miles and it ran really good and in the next 4 yrs. I ran it to 320,000 all highway and it still ran well, when I sold it here a couple of months ago.
I never changed the oil myself
I always had it done at wal-mart using whatever they had on special.
Although I'd never let them change the oil in my bird.