FWIW, I have been experimenting this summer with different weight oils - - changing them at 1000 mile intervals.
The engine sounds and shifts so much better with 15w oil - especially at higher temps. Since I'm a Mobil fan as of late, I've been mixing 50% of 10/40 and 20/50 to end up with 15/45 ish. 15/40 MC oil is hard to find.
The chain tensioner shuts up faster, and the whole engine just sounds and feels more 'solid' - especially at higher RPMs.
Midway through doing this I read about the change to 15/50 in some markets. Seems like a good idea. The only downside I can report is slower starting on cold mornings (low 40's are the coldest I have seen so far.)
Oil thread MF'ers!