Translation of "Mirage" in French

A mirage is said to be an illusion.

On dit que la Fata Morgana est un mirage.

Which makes me think it was definitely a mirage.

Je pense qu'effectivement, c'était un mirage.

The water on the road was just a mirage.

L'eau sur la route était seulement un mirage.

And that just makes me a little bit suspicious whether maybe, the oasis is really a mirage.

Je me demande si l'oasis ne serait pas en fait un mirage.