When to declare emergencies?

[xwhitemousex]

Thanks for clarification.

You might be right about the pitot heat... I usually turn it on, but might have missed it. And I was flying in Alaska so there is a good chance it was cold enough that it froze.
Guess that is why we have, and should use, the checklists :P

I suppose any malfunction called out by the co-pilot, as you might have heard him do in the video, should be declared.

But what about more sneaky malfunctions, e.g. oil pressure drop, overheating or slow fuel leaks? Are those grounds for declaring an emergency?