Oil questions

Hopefully someone can give some input on this. We have a 2001 Caddy Deville with about 112,K miles on it. More recently the car has been using a lot of oil. It doesn't leak any oil on the ground, nor does the car physically burn the oil, it just simply is gone! Normally by 3,000 miles there is very little left. The dealer says this is common, and that carbon build causes this. The car gets driven daily with mixed driving highway and city. I feel like there is something else wrong... does anyone have some ideas?

This is a common issue with that N'star. Carbon accumulates on the oil rings and they cannot expand against the cyllinder wall to seal out oil migration. There are several tsbs on this from a decarbonizing procedure to a re-ring.