Here's a link to a previous discussion in the forum addressing engine break in:
https://dodgechallenger.com/forums/m...k/tm.htm#17494

I was told/taught to vary the speed as much as possible for the first 5000 miles - no cruise control, and as few InterState miles as possible. I also avoid hitting the rev limiter, and excessive idling during the first 6 months with a new car. Change the oil after the first 1000 miles, then again every 3000 miles - religously. This practice has never failed me. I've never suffered engine problems with any car I've broken in this way.