DALE - What the heck is Dexos? O-K, I googled it...
I had a '99 Chevy Lumina sedan w/3.1L V6 that came from the factory with synthetic oil in it. I used Mobil 1 full synthetic in it for 82,000 miles and traded it off. I suspect it's still running with 300,000+ miles on it. The engine was the best part of that car.
My '96 F250 had full synthetic oil in the transmission, transfer case & frt & rear drive axles from the factory.
My '06 Volvo S40 with the turbo-charged 2.5L in-line 5 cyl engine actually recommends Castrol synthetic oil in the manual, but I use Mobil 1 as do probably 75% of the owners in the US. Car has 133,000 miles and has NEVER burned a drop of oil.
So Yes, I would say most auto mfg's recommend full synthetic engine oil.