I have a 2010 Terrain, worst car I ever owned. Had GPS problems from day on and they said they fixed it and never did and always acted like I was crazy, Finally the warranty ran out when I was not paying attention, so I wrote to GM, they have a complaint person and she got it replaced. Everything is fine and about a year later I get a letter from GM saying that the radios are having problems and they will fix it even if it is out of warranty. So basically the dealer knew all along.
Had the same experience burning oil, I was going thru a quart every 1000 miles, so they make me go thru all these oil consumption tests which wasted a lot of my time and they finally fixed it. I asked what the problem was and they said it was collapsed rings, and it happens all the time with that engine. SO they knew all along.
Then there was the stretching timing chain, which made the car sound like a world war I biplane. And the clicking water pump.
Not their best effort. My problem is I am busy and do not have time to mess around at dealers