10-30 vs 10-40 oil

[HikerToo_imp]

I went with the HP4S full synth 10/30 in mine, hope to get 4K miles out of it between changes.
Since the user manual only had 10/30 listed, that's what I went with, if I had known the service manual also approves 10/40 I probably would have went with that for the summer months, and 10/30 for cooler months.
Then again, the engine is new and tight, so maybe 10/30 IS the best way to go for now, regardless of outside temp?
I chose Full Synthetic thinking the air cooled could run hotter and Full Syn will withstand high temps better.