https://www.avweb.com/ownership/shoc...kill-the-myth/
Avweb agrees
I like the point that the ultimate shock cooling is engine shut down.
Lycoming says:
https://www.lycoming.com/content/how...ng-your-engine
No more than 50 degrees per minute
And about cold starts:
https://www.avweb.com/ownership/cold...ing-it-slowly/
Looks like the definition for cold start is below 20 degrees Fahrenheit. All kinds of machinery (and people) have problems in that temperature (as experienced with the record setting cold snap across 1/2 the US this week).