when oguz were still a tribe they could understand much more from qipchak language. Oguz was close with Persian empire, and when Persians had civil war , when persian royaliry friends of oguz lost, they took revange and wake up in the head of persian empire and formed The Great Seljuks empire. Oguz loved persian culture and thier language suffer many changes tooking persian words. After The Seljuks , Ottoman royality was using persian language for speaking and writing. And Crimean tatars with qipchak language , after alliance with ottomans , they have "turkisficated" thier language.