Some more quotes. Maybe they can be useful, though it's Clark speaking, not Superman. I know they're the same, but you know what I mean, don't you? :p
From Neverending Battle:
Lois: How long can you hold your breath?
Clark: A very long time.
From Ides of Metropolis:
Lois: You know I have a funny feeling you didn't tell me your biggest secret?
Clark: Well, just to put your mind at ease Lois, you're right, I didn't.
From Operation Blackout:
Clark: People can have two sides to their personalities. Lois, believe me, I know.