synthetic oils?

I have a 300ex and im needing to change my oil again, and i want to put in a synthetic this time and i run it in the spring summer and fall, and rarly in the winter. im not sure what i need, 10w40 or what. and im not sure what brand will give me the best protection. what have been your guys impressions with synthetics? thanks guys Brent,

[Deathbringer]

Without a doubt this has been covered TEN THOUSAND times... you need to search a little before posting...BUT...that being said.

Mobile1 15w-50, I use it and no probs at all...great oil