I just bought a new transmission for my '03 G35 6MT. The new transmission is the latest revision, Part No. 32010-CD009. My mechanic, as well as two dealerships, told me that you're supposed to use 80w-90 fluid in the transmission. But my 2003 owner's manual, and every manual since 2003, says that you're supposed to use 75w-85 or 75w-90 fluid. So, two questions:

1.) What's going on? Does the new transmission revision just call for thicker fluid than the old ones did?

2.) Who even makes an 80w-90 transmission fluid? I'm pretty sure Nissan doesn't...