Should a model method call 'save' itself?

Let's say that we have a method inside a model that

1. needs to called only on saved records
2. may update the model itself and thus the model needs to be saved again afterwords

Should the "save" calls happen inside the method itself like the following code

def result
  save! if new_record?

  # do some funky stuff here that may also change the model state
  # ...
  # And calculate the return value
  search_result = "foo" # Let's say "foo" is the value we calculated

  save! if changed?
  search_result # return
end

Or should the external observer (the controller) be responsible for calling save as needed?