Afraid I remember very little of the story, except for the ending. I'm hoping that is memorable enough that someone will know this one.
A group of astronauts/space travelers are on a mission to rescue another human, who is either trapped on a space station or in a lifeboat/pod of some sort. Again, I don't remember many of the details. There is some sort of peril involved, however. The human to be rescued has his faithful robot assistant with him. I don't remember the robot's name, but let's call him "Roboto", for argument's sake.
The ending to the story - the one part I can really remember - is chilling. The rescuers eventually reach the station or lifeboat, and find the robot by itself. When they question it where the human is, the robot replies something like "Lubricants. With our metal joints and many gears, robots need them in abundance/frequently. I could not wait any longer. The human body is an excellent source of lubricants. I can assure you [person's name] died quite painlessly."
The story then ends with a final line tacked on to it. In all caps, there is a sentence that goes something like "ALL HAIL ROBOTO, LIBERATOR OF ROBOTS!" The thrust being, the events in the story led to all of to a robot revolution against humanity. The story is being told in retrospect. I always thought it a rather clunky and silly addition, marring the excellent ending, but that was the last line in the tale.
Timeframe of Publication
Not sure. From what I remember of the tale, I think it is a very old story, probably no later than the 1950's or 60's. Possibly considerably earlier.