In theory and what they all say, you can run more miles on a synthetic oil than old dino. We used syn oil during the last oil change.
My wife does 60 miles a way, 95% highway miles on the car. The oil life meter says that there is 27% life remaining and my wife wants to change it today.

Now since the OLM is based on a straight old algorithm there is no way the car knows if I've used dino or syn. I don't like wasting oil and I think 27% still has miles to go on the oil, plus the syn people would say that I can go further than the OLM.

On some cars (think my son's Saturn is one) you can run the OLM down to almost zero and if you do so, the manual suggests changing the oil within the next 500 miles.