Since I am always looking for the correct and best products for the least cost and the best availability, I thought I would post on here what I have found for another oil filter option and transfer gear oil.

Finding oil filters isn't that big of a deal since there are so many aftermarket brands available. I've seen other post on here that showed some concern on using automotive filters because of higher bypass valve opening pressures. I've mentioned this filter before but just found the pressure specs on it. After a little research I found that Nissan part# 15208-65F0C fits and at 14psi it falls in the center of the Yamaha pressure spec of 11.3-17.1 psi. 15208-9E000 is the same filter but a bit longer for more capacity.

Transfer gear oil is a different story. Yamahas specs for it is "SAE80API GL-4 hypoid gear oil". According to this link, Gear Oil Tech, GL-5 lube IS NOT compatible and and is corrosive to some metals (mainly copper/brass). It also mentions that some think that using synthetic GL-5 is ok but in the case of synthetic it just depends on which additives the company used. In other words, if you use synthetic GL-5 you are rolling the dice and taking a chance.
Sooo, here is what I found. I know Nissan part# 999MP-MTF00P 75w85 MTF is GL-4 rated. Also, Spectro makes a straight 80w oil called Spectro Golden Gear Lube that is a GL-4. The problem I have found in running down GL-4 lubes is that a lot of the manufacturers don't list it as GL-4 on the bottle... they just leave off any type of rating. But, all GL-5 lube, that I have seen, has the rating on the bottle.

FYI, this is my understanding of the material that I have read. And I'll be using the Nissan products since those are available to me. Feel free to do your own research and make your own choices.
Hope some of this helps.