In the history of the series, nearly every last character has stated "and I'm almost/running out of chakra" and I mean other than maybe once or twice in the manga, even if that at all(can't remember) Naruto has never been out of chakra and neither has Kurama. In the final clash we get to see Naruto with no chakra/what it's like when Naruto is actually running on E. Interesting, Naruto solos