Another thing I was concerned about, currently 116K. I saw one for sale on Marketplace for cheap, w/a broken timing chain @ 133K.

Timing chains don't often break for no reason, and if it was a defect it would have broken probably more than 122,000 miles ago.

133,000 miles and a broken timing chain has some kind of dreadful backstory for that car.

I wouldn't worry about this issue on yours. Change the oil with good stuff at least every 5,000 miles and it will likely last a long time and maybe never have a timing chain issue.

Boilerplate: No guarantees, individual results may vary, void where prohibited, professional driver on a closed course, yada, yada.

Don't buy the car. That engine and possibly the tranny will need replacing. Does the owner have driving age children?

I'm not buying the one with the broken chain, I was mainly wondering if the 4cyl was an interference engine, and would it be recommended replaced by a certain mileage. Just going by 4cyl.'* in general.

Yes, it is an interference engine.

I haven't heard of these ever eating timing chains, except in cases of poor maintenance and/or abuse. If the tensioners go bad, it can skip a tooth and cause running issues. If it skips a few teeth it can damage things internally. If it skips a tooth, it will run poorly and light up the check engine light.

Timing chains and tensioners really like clean oil. Keep up on that and it should last a while. If the oil is coming out pitch black at whatever interval you do it, do it a thousand miles sooner next time around. I look for it to have just a little color left when it'* draining.

Since the dealership is claiming a bad timing chain, I did some research. And apparently, timing chain issues are pretty common on these Ecotecs. This seemed to sum things up:

"What years did GM have timing chain issues?

While 2.4 liter GM Ecotec engines are known for having timing issues, they are notorious for the ones made from 2010 to 2016. Especially the ones found on small to midsize SUVs, such as the Buick Regal, Buick Lacrosse, GMC terrains, and Chevy Equinox.

Final Words

No engine is perfect, and that implies to the GM’* 2.4 Ecotec engines. Though you have seen the GM 2.4 Ecotec engine problems, it is an excellent choice for you if you are looking for a good balance of efficiency and power.

While the 2.4L Ecotec engines are plagued with excessive carbon buildups, timing chain failures, high oil consumption, and oil leaks after covering high mileage, it is not big enough to say it is a bad engine. Certainly, the 2.4 Ecotec are not the most reliable engine within its range, but they are still a good choice for your money."

This seems like an A.I. response. Where did this come from?

The Ecotec 4'* do have some oiling issues, but bazillions of them were okay. I have a hard time condemning one based on a generalization.

I am curious: What did they say is bad about it the timing chain on yours? What code(*) did they find and/or what diagnosis did they perform? Generally a P0016 would indicate excessive timing chain stretch, which is generally the most common thing that goes wrong with timing chains on modern engines that doesn't involve loud noises and a tow truck.