Hey Scotty. What do you think of using motul motorcycle oil to help your engine last a long time. Specifically a Yamaha xsr700 twin?
That's a good oil but practically, any oil with correct viscosity does the job as long as you change it with the filter regularly.
I always used Castrol 20w50 in all my bikes.
If you want to get technical, the thing you have to watch out for is "friction modifiers" which are added to some newer oils to reduce friction - but may make your wet clutch slip. Fortunately, all you have to look for is JASO MA or JASO MB on the label, which is the American Petroleum Institute standard for wet-clutch use.
https://www.oilspecifications.org/articles/JASO_MA_JASO_MB.php
Like Doc, I have been happy with 10w- 40 or 20w-50, depending on the manufacturers recommendation and temperature, which is what Yamaha recommends on page 9-1 of your owner's manual -
"API service SG type or higher, JASO standard MA"
https://library.ymcapps.net/library/om/contents/pdf/10/B2G-28199-13_02.pdf
