Which coolant should I use I had a coolant leak

I haven't drove my car in awhile because of the leak so which coolant is best to use I was just using the green antifreeze

If you have a leak you should use a very weak solution of anti freeze and water until winter

Use a coolant that is safe for aluminum.

For a 1990 model GM use the traditional green antifreeze or anything that says "all makes/all models" on the bottle. Hope that helps! Jim