"Other than" means except while "rather than" means instead of.
For example, these two are very different.
facebook is the most hyped thing this year
other than the iPhone
This means that facebooks is the second most hyped-up thing this year (while the iPhone is the first).
facebook is the most hyped thing this year rather than the iPhone.
This means that facebooks is the most hyped-up thing this year instead of the iPhone.
other than
prep. With the exception of; except for; besides: Other than one sister, she has no close relatives.
adverbin another and different manner; "very soon you will know differently"; "she thought otherwise"; "there is no way out other than the fire escape"; [syn: differently]
rather than
conj. And not: "Gibson guitars—with their carved tops and necks that are fitted and glued to the body, rather than bolted on—are expensive to make" (Joshua Rosenbaum).
prep. Instead of: "diseases in which the immune system plays the villain rather than the protector" (Sandra Blakeslee).
If you wish to say "Use fuel
but not gasoline", I would suggest "
rather than".
If you wish to say "the presence of elements
besides iron", I would suggest "
other than".