Can't believe that I can't find this in a search, but here it is: which weight of oil do these cars like in warm weather? 20W/50? 10W/40? It's an '89 w/ 120k miles if that makes a difference.

I haven't owned this engine before, so I am not familiar w/ it yet. Does it have hydraulic lifters? (No valve adjustment)? If so, I would imagine that the correct weight of oil is very important. The owners manual gives several choices, but I'm sure that people here can give me some informed opinions. TIA.