Here are 5 UOA's from my 2000 4Runner which has the same 3.4L V6
http://home.illicom.net/users/jsharp/personalphotos/OA/Toyota_oil_anaylsis_5.jpg
Oldest 2 are M1 5W-30
Next 2 are GC 0W-30
Last one is M1R 0W-30
All of these oils work fine in that engine. I doubt you'll do any better using a 10W-30 or something heavier.
http://home.illicom.net/users/jsharp/personalphotos/OA/Toyota_oil_anaylsis_5.jpg
Oldest 2 are M1 5W-30
Next 2 are GC 0W-30
Last one is M1R 0W-30
All of these oils work fine in that engine. I doubt you'll do any better using a 10W-30 or something heavier.