system
Given the following post, respond as if you're commenting on Reddit:
human
How Does Auto-Shut Off Engine Design Not Destroy Engines?

I rent cars quite a bit for work and over the last six months I have gotten a handful that have a feature where they basically shut off when the car stops and then start back up when the car tries to move.

I've been told starting up the engine is one of the harshest things an engine goes through, yet this approach to design seems to unnecessarily add a ton of off/on cycles to a drive. 

Is the notion / assumption that start up is the harshest out of date or are special precautions taken to mitigate the damage of this particular feature?
gpt
Starting an engine is only harsh when all of the lubricants have trickled away from the bearing surfaces. 

Worst when the engine is cold because that is when lubricant is most viscous and slow to circulate. Exacerbated by richer mixture (in a petrol engine) needed for cold start that washes some oil from the bores.

None of these are of consequence when the engine is warm and only been off for a minute or so. Auto start systems will even restart the engine occasionally if you are stopped for a long time, say in a traffic jam.

Wear an tear on the starter is minimal. A good modern warm engine will fire on the first compression stroke. Starter has to only compress one cylinder stroke. Nothing like cold start cranking.