Lower unit grease type

I have always used Yamaha oil and lower unit grease. Does using the Yamaha brand in a yamaha motor matter. I have a half hour trip to ther yamaha dealer but have Mercury dealer right in my hometown. So question is  How important is using the Yamaha brand in a yamaha motor?

For lower unit oil I'd stick with OEM if it is under warranty.  

If it is not under warranty, there are lots of quality options.  I put Evinrude Etec lower unit oil in my Etec as well as my Yami.  I'd do it the other way around too, just happen to live close to an Evinrude dealer so it's convenient. 

Most importantly, never mix oils.

If it's only a 30 minute trip would stick with OEM fluids if it's a newer motor. Myself use Mystic brand from Fleet Farm for a few years now and have no issues, but I have a 1984 Evinrude on the back of my rig  . Most Oils are all certified so there is not much difference between aftermarket and OEM . Some have different additive packages that very slightly between brands . If your motor is under warranty yet I would stick with OEM