Can you trust oil light use on "05 Cobalt?
If you SEE the oil light, you can trust that you are about to destroy your engine.
The 05s do have an oil life monitor. If that is what you are asking about. I don’t know how sophisticated they are. I have 2013 and generally prefer to change when 20% is indicated.
You look at miles and the indicated percent and see they compare. You can always go by miles driven if you wish.