> How long will the engine and transmission actually be good for?

Fortunately, there's a ton of data out there. Some manufacturers/models are known to be reliable. Just hone in and buy those.

I've had to do repairs, but never that expensive. Never had transmission issues (keep in mind my cars are often over 10 years old - one over 20). For engine stuff, it's just a part replacement once in a while.

I posted elsewhere, but since 2008, my average car expense is about $450/year - that's repairs + oil changes.

> How much will replacing it cost?

Individual parts? Usually, not much. The whole engine? Dump the car. You got a lemon. Did you get it checked out by a trusted mechanic before buying?

> At least with a battery you can get some pretty detailed state of health readouts, BMS technology can tell you a good bit more about battery health than what your ICE will tell you about transmission and engine wear without tearing it down.

Fair point.