It doesn’t say that if you don’t use Yamahalube oil nor does it say that any other oil will invalidate the warranty. What it does say is, (and we are talking about oil only here), is that if the oil specification does not meet that recommended by Yamaha, only then would the warranty be invalid. Therefore, you can use any oil that meets or exceeds Yamaha’s specifications whether it is called Motul, Mobil, Shell, Citgo or Walmart Super Oily Stuff!
Almost like the difference between "recommendation" and "requirement" is not understood, whether on purpose or not is another matter of course.
re·quire·ment | \ ri-ˈkwī(-ə)r-mənt
\
Definition of requirement
: something
required:
a
: something wanted or needed
: NECESSITYproduction was not sufficient to satisfy military requirements
b
: something essential to the existence or occurrence of something else
: CONDITIONfailed to meet the school's requirements for graduation
something required:; something wanted or needed : necessity; something essential to the existence or occurrence of something else : condition… See the full definition
www.merriam-webster.com
Vs
rec·om·men·da·tion | \ ˌre-kə-mən-ˈdā-shən
, -ˌmen- \
Definition of recommendation
1a
: the act of
recommending
b
: something (such as a procedure)
recommended
2
: something that
recommends or expresses commendation
the act of recommending; something (such as a procedure) recommended; something that recommends or expresses commendation… See the full definition
www.merriam-webster.com
Not that I think it'll help, but just in case.
To use the words in a sentence: Yamaha is making a recommendation to use their oil, but for warranty it is a requirement to use motorcycle specific oil, such as JASON MA or MA2.