In his epic, what did Gilgamesh want to learn from Utnapishtim?

The king who could conquer men and monsters could not stop his friend from perishing. Overcome with grief and helpless before the inevitability of his own death, Gilgamesh abandons Uruk and begins a search for Utnapishtim, the man who survived the great flood and was granted immortality by the gods. If only he can learn the secret of Utnapishtim, he too might live forever.