Actually, you do not use any oils with a grade higher than "CD" and do not use oils labeled "Energy Consumption II." I think LB already mentioned this limit. The reason for not exceeding this specification is to preclude starter clutch slippage. (Page 6-2 of the '04 Operator's Manual.)
Also, there use to be a few posts regarding full synthetic oils causing starter problems. However, I am not sure we ever pinned the exact oil specification down.
Personally, I stick to the OEM recommendation. For the '03 and '04 that was the 5-30 Four Stroke Oil. Last year, I had to ask for it, as they no longer keep it out on the shelf.
I will add that I have over 10K miles and no oil consumption issues. But I also use Ring Free and occasionally hit her with Seafoam too. You got to keep the carbon off those rings.