Synthetic oil. Can it Really Go 10,000 miles?

[bronsin]

It's being claimed that conventional motor oil needs to be changed at 5000 miles and The synthetic can go 10,000 miles. In the past experts said it's the additives that wear out in motor oil thus requiring it's changing. And in fact even regular motor oil once it's been changed can be refined and used again. So if it's the additives that wear out and the oil itself can be refined and reused....what's preventing the additives in synthetic oil from wearing out just like the additives in conventional oil wear out?