Oil loss in 2005 cadillac

The oil is being burnt during combustion.
Time for a new motor

Ouch

Any signs of blue smoke?

If there's blue smoke, this means it's burning oil. That might mean bad rings and VERY expensive engine work/ engine rebuild or replacement. I'd get a compression check by a certified mechanic.

However, there could be a possibility of leaking valve seals if the oil was blowing out as unburned. You 're certain you see no signs of leaks or some sort of dark smoke at all?

Have you had someone follow behind you in car, perhaps?

I'm no mech. expert, there's a few things to go on.

If you do a search on Google using keywords "2005 Cadillac loses oil" and you might find that you're not alone:

"a 2005CTS - 3.8 They have oil consumption issues"

You make a pretty wuse decision .