Jim C.,
Regarding your question posted 1/28 @ 4:44pm;
I'd suggest you follow what is recommended in my CC 129 Owner's Manual....
"...the selection of crankcase lubricating oils should be based on the lowest anticipated temperatures until the next drain period."
As far as using a different weight/type of oil than what is recommended by your Owner's Manual affecting your warranty, I'd suggest you stay with what YOUR Owner's Manual says to use.
However, I'll go further & say this - I've never known/heard of ANYONE that has experienced an engine failure that was due to the use of a "non-recommended oil type". ALL engine problems related to oil that I've heard or known about were due to only two reasons. Either:
1) LACK OF OIL
or
2) LACK OF OIL CHANGE FREQUENCY
So, if you simply check & top off the engine oil level every time before you run it (or as the manual says, every 10hrs of run time) and change it every 30hrs of run time,,,I HIGHLY DOUBT you'll ever have a oil-related engine problem.
Good Luck!
Ryan W