Watch out for direct injected cars, which is virtually all of them now except for electrics. Many don’t have traditional fuel injectors in the intake manifold anymore, and because of poor PCV systems, oil vapor carbonizes on the intake valves, causing problems. This is generally around the 40k-50k mile mark, potentially sooner if people don’t drive their cars on the freeway for extended periods after startup. Some newer cars have addresses this by adding supplemental fuel injectors in the intake (some audis, some Toyotas) but it’s not a widespread practice, of it will ever be.