How do modern cars regulate temperature so well?

From what I can see in this discussion is no one addressed the fact that the older cars aren't actually "regulating" anything. Regulation requires some "smarts" being built into the system. Older cars "attempt" to do it with what they had. Water hits a certain temp, fan starts in order to stop the rise, or bring it down etc, meanwhile the temp is rising because, that ramp up has already begun and it's not easy to stop, eventually, it will happen, but then the water might cool too much and the cycle starts over. The problem with this is of course, the timing of it all. It's like a diabetic who take insulin right before eating instead of 15 minutes before. You have to try to match the curves and the older stuff just isn't up to the task.

Nowadays, temperature control is often done with a PID loop. The system uses a controller, which "knows" based on the current temps, and rates of change measured by the differneces in the current and last few measurements, how to predict when to start and stop the fan. Doing this, you get a far greater accuracy than a simple on/off that's activated on a general temp.