2006 Cadillac CTS

You blew the heads or did you spin a bearing?

Had there ever been any concern of oil consumption, or rough run that was a result of low oil level? The acceptable rate of consumption is 1 quart in 2000 miles as illustrated in GM bulletin 01-06-01-011D, and you vehicle has no oil level sensor. With that being said, this is an exerpt from your owners manual, under the maintenance heading, that would release them from any liability for warranty. This would especially be the case if you had no, or limited, history of doing business with your GM dealer.
At Each Fuel Fill

It is important to perform these underhood checks at each fuel fill.

Engine Oil Level Check

Notice: It is important to check the engine oil regularly and keep it at the proper level. Failure to keep the engine oil at the proper level can cause damage to the engine not covered by the vehicle warranty.

Check the engine oil level and add the proper oil if necessary. See Engine Oil.

Engine Coolant Level Check

Check the engine coolant level and add DEX-COOLÂ coolant mixture if necessary. See Engine Coolant.

Windshield Washer Fluid Level Check

Check the windshield washer fluid level in the windshield washer fluid reservoir and add the proper fluid if necessary.

How low was the oil when the engine blew? That is usually the problem. If there are oil consumption problems it normally is valve seals and sometimes piston rings but not often. What specifically is wrong with the engine? Did it overheat and you kept driving? But you really need to know how much oil was in thesystem, that is a primary cause for engines blowing, they get to low on oil and a little bit of aggressive driving can do this.