Left the house, coasted through my neighborhood and was sitting in traffic when the engine started shuddering, so I pulled over and it died. Started it and it ran awful so I turned it off. I used OnStar for roadside assistance and they sent a flatbed to transport to my dealer. Tow cost me nothing.
I showed the tow truck driver the tow hook, and we used it to get the car on the trailer. Had just enough clearance. The driver took photos and said this was his dream car. He took good care to secure it.
Dealer said they found coolant in cylinders and claim it's a blown head gasket. Obviously, we are all aware of collapsed lifters. I didn't hear the classic lifter tick, it just ran awful. So we will learn more once they pull the heads. I asked them to give me a call when they do so I can come take a look at any damage.
Additionally, I informed the dealer that I had filled my fuel tank less than 1/4 mile before the engine ran awful. Then a few days later that gas station had all of those pumps taped off. I went in and they admitted they have an issue with their premium tanks (Top Tier Phillips 66). I gave them my contact info and asked they let me know what they find, but I expect I need to follow up. This wouldn't explain coolant in cylinders, but we'll see what happens.
My dealer has been great. They have parts ordered and expect to tear into it next week. They gave me a 2024 Trax Activ as a loaner. Obviously, I'll report back with the results.
Given my driving habits, this car has spent A LOT of time in V4 mode. My 50 mile MPG best is 38.4. I did the break-in properly, and keep up with oil changes using the correct 0W-40. I've paid a lot of attention to the AFM system, and I expected to add a range module after the warranty was up. We'll see if AFM had anything to do with this, there was a switch to/from V4 when it ran rough.