Add another engine failure to the list. Engine failed at only 167,000 km (104,000 miles) despite extremely meticulous oil change intervals (6-7k km) and religiously-followed overall maintenance. The car never gave me a problem and drove very well until I had noticed low oil levels/dark oil in between oil changes starting around 130,000 km. Dealer advised that there were no noticeable oil leaks and to diagnose the issue (partial engine teardown) would be $400+; they recommended to keep an eye on the oil level and fill when needed. Fast forward to 167k km and without any warning while driving home from vacation (oil level fine before leaving), my check engine light started flashing and my car went into limp mode. Oddly enough, there was no ticking/knocking/smoking. I was able to pull over and get towed to a local dealer who determined my engine was shot. Luckily I had completed the knock sensor recall and had all my oil change records, which qualified me for a free engine replacement and rental car in the meantime, but who’s to say this won’t happen again with the new engine. Buyer beware with these engines - even with closely-followed maintenance and checking/filling oil that these are prone to premature failure. If you do have one, make sure you have the knock sensor recall performed and make sure your oil change records are available.

With 1/4 tank of gas, the car started bucking and losing power as if there was no gas at all. Pulled over to side of highway on an exit ramp and let it sit. Car would not restart or would run only for a couple of seconds. There was no check engine light. Car had been burning a lot of oil in the months prior to the event, most recently a quart every 700+ miles. There were no oil leaks observed nor any smell, so it was being burned somehow. The oil level at this event was between the two dipstick marks.

I had car towed to a nearby garage who eventually did some diagnostic work and was focusing on one of the middle cylinders not firing. Spark plugs were all clogged up. Direct injectors were functioning normally, and fuel system was okay. So I ad car towed to a more local garage who concurred with the first one's diagnosis and further determined that that there was no compression in suspected cylinder; however there was no carbon build-up in the valve head area. Valve cover gasket was leaking.

The month before, I had been mailed the Theta engine lawsuit settlement notice which simply said that the 2017 Sonata was part of the extended short block warranty and did not specifically exclude the Gamma engine. However, since my engine is a Gamma II engine then it was denied when I tried to register a claim. It is the opinion of the 2nd garage that there is probably connecting rod failure. Had car towed to Hyundai dealer who (after a week) has yet to provide me with a diagnosis. I filed a complaint with Hyundai's case management department and after a week of pestering them, the case manager "Judith" has yet to call me back. If my Sonata has a different engine then I never should have been mailed the Theta settlement notice in the first place. Since then, I have had to rent cars for my work and have over $1K in diagnostic charges with no end in sight. Hyundai needs to make this right and don't intend to let them get away with this. I have owned many cars over the years including other Hyundai's, many over 100K miles, and none have ever had major engine issues like this.

Update from Dec 22, 2021: 12/22/21 - Hyundai of Lancaster (PA) has, at the request of my Hyundai America case manager, requested "Assistance" from Hyundai America, meaning that they're asking the corporation for permission to replace or repair the engine without cost to me. If granted, and I'm not holding my breath, I would also be reimbursed for car rentals as well. In the meantime in a couple of weeks I'm going to have it towed to a trustworthy local garage to have it evaluated for engine repair.