" Gear Case oil should be changed after the first 3 months or
3,000mi., whichever comes first. Gear Case oil should then be
changed every 12 months or 20,000mi. Use only NONsynthetic
80W-90 GL-5 gear oil.
The Gear Case should contain 6 oz."
That is why I had it changed this year. Its been changed twice in less than 13000 miles. Did not want a warranty issue.