My belief, when it comes to older cars, is that frequency of oil changes is more important than the oil itself. Of course there’s little to no science to back it up. But I figure all the little wear the fancier oils are suppose to protect your car from, have already happened in an older car. So I just change my oil at 5k on the dot instead of 7.5k with good oil. Of course frequent oil changes with “good” oil are ideal.
Plus, I don’t know if this is true, but growing up I was taught the quality of the filter is more important than the oil itself. And I always use good filters.