OK so I've been reading about these catastrophic engine failures and now I'm paranoid. It seems the typical scenario is a sudden, rapid increase in oil consumption. This goes unnoticed and engine failure naturally follows.

My question is this:

Why is the low oil not discovered before there is engine damage? It looks like the low oil warning light would come on and warn one before things got so permanent. Or doess the low oil light just mean low oil pressure - not oil level - so it only comes on when the pump starts sucking air? If that's the case is there an aftermarket low oil level warning system available?

Thanks for any insight you can provide.