I took it that Fury Road sort of was a reboot as he loses his original car again and lacks the physical scars and signs of aging he had in the trilogy.
The whole series has never concerned itself with continuity. One popular theory is that the 'real' Max was in the first film but each subsequent film is essentially an urban legend of that person. In theory the Max of film one might not even be the same person as depicted in film two. Almost a Robin hood type of character.