Tuesdak
TDR MEMBER
Hard decision. I’ve got brand new Michelin’s, spare wheels and a lot of knowledge for a DTS....
So you know "NorthStar" = "$Headgaskets$" regardless of GM's finally fixed/improved (2004+) after a decade of throwaway NorthStar engines. A HG job would cost book value on that car. Cadillac may have a rep for luxury, but, it also has a rep for high priced repair parts and a bad rep for unreliable engines. Oldsmobile, may they RIP, built more reliable engines and even the Olds 5.7 Diesel hand-grenade was almost on par with typical Caddy engine failures.
Whats the coolant service history on it? You have a test kit to see if there is combustion gas in the coolant? I bet the oil pan leaks on it. Don't NorthStars hold 7+ quarts to just "make it" between oil changes between high consumption and leaks?
Buick will get you down the road with less parts need and less expensive parts at that.