Interesting question you pose. My question is how many folks here have frequently driven cars well beyond 100K miles? If you trade in early, you may never see the benefit of synthetic oil, except as a selling point. I sold my sister my 1993 Altima at 125,000 and it has nearly 300,000 miles now without requiring any engine work. Synthetic oil responsible? Of course I cannot say definitively.

Any way, I still prefer following the manufacturer's recommended interval with synthetic as apposed to those who change their dino oil every 3000 miles "just to be sure". (I wonder if I'm helping to save the synthetic dinosaurs, or just providing extra funds for the synthetic Middle East?)