thats the thing... no one can safely say when it is safe to make the switch to synthetic... it all depends on the engine, how it's maintained and how the seals are...
personally at 60k I would make the switch to synthetic on a duratec... the SHO tho - nothing but Gastrol GTX (maybe even the high mileage formula) for the rest of its life.
plain and simple, use good oil and filters (k&n or OEM) and change them often!
using synthetic on my duratec I changed the k&n filter every 5k and the Mobil 1 oil every 10K. It looked brand new at 10K even
