AngryScotsman

Probably a few reasons:
1. If the oil is doing what it needs to do, why change it?
2. Unnecessary environmental waste
3. Saves you money/time


Changing your oil more frequently/less frequently won't change carbon build up.

CaliBenzDriver

well actually now we have the option to stop carbon build up. When oil is not vaporized, it stays in the engine instead of coating valve stems.

Once oil is burnt, its viscosity drops towards the bottom of the W30 range. That's when engine needs chemical lube to protect bearings with low pressure.

My engine that had been ingesting quarts since factory new is no longer loosing one drop.

We have simple options to preserve our valves and SMOG fumes.
We can call that good old legacy cooling.


Cleaning valves without fixing the root cause is a band-aid