I figure I misremember the details and that it wasn't "enough fuel for 120 days" because it would be just too silly to state that it wasn't enough to cross some desert.

Yee...ess, Nux was showing signs that his 'metal head viking warrior' demeanor was a bit shaky, so I guess that when his Valhalla dream got shattered, he was ready to choose a new path to glory. Maybe. ^_^