synthotic oil

I run the Mobil1 full synthetic for performance engines , or the enhanced performance version along with the KN filter as per my engine builders instructions , I just ran 10,000km in less than 2 weeks almost all highway between changes and the stuff works great.
I can only get the first one in 15-50 so it is my summer oil and the the latter I get in 10-30 or even 5-30 for the colder months .