Carpenter Mike

How would the "warranty department" know what oil viscosity you used? I also find myself doubting the wisdom of 0-20 weight oil. It sure seems thin as water when I do an oil change, and super black after only 3000 miles....

As far as the motor being in 4 cylinder mode, the only time mine is in 4cyl. is when I'm coasting down a hill. The 4cyl. mode doesn't have enough power to get out of it's own way, total joke....

My 2017 Sierra Denali is also doing the same thing, usually notice it after going around a corner just after I lift my foot off the brake and start slowly accelerating. Perhaps it's going into second gear without enough fluid pressure to complete the shift in short order. At first when it started doing this, I though there was some "washboard" in the roadway, but it seems to be happening in every corner. I have 26,000 miles but the warranty is long gone. I'm thinking about selling it before it breaks and leaves me with a big bill....