>There's "nothing worth clicking on" for question 1 because it's arguably (certainly so in my opinion) a worthless question. Without at the very least providing the specific model of car, even an experienced mechanic will struggle to answer it for you meaningfully as phrased - there are a huge range of recommended oil service intervals across different car models.

Doesn't seem too hard to generate a bunch of content marketing articles for "how often to change oil for {2012,2013,...2026} corolla", similar to how there's content marketing spam for every windows error message imaginable, which end up being some variant of "have you tried sfc /scannow?".