upkeep vs fixing

upkeep and fixing both are nouns.

Word	Noun	Adjective	Verb	Adverb
upkeep	Yes	No	No	No
fixing	Yes	No	No	No

As nouns, fixing is a hypernym of upkeep; that is, fixing is a word with a broader meaning than upkeep:

Other hypernyms of upkeep include fix, fixture, mend, mending, repair, reparation.

upkeep (noun)	fixing (noun)
activity involved in maintaining something in good working order	the act of putting something in working order again
the act of sustaining life by food or providing a means of subsistence	the sterilization of an animal
	(histology) the preservation and hardening of a tissue sample to retain as nearly as possible the same relations they had in the living body
	restraint that attaches to something or holds something in place