After Ford's lawsuit around its Ecoboost 2.0 and some annoying transmission quirks (the dealer and two different trans techs could never find the cause) I traded my 13' Fusion for a 2021 Mazda3 Sport 2.5 AWD (no turbo)
The manual really doesn't say a whole lot about breaking the engine in besides not to stay at one speed too long and not to rev it. But it doesn't specify how long.
When would it be safe to take it for a long road trip or do some more "spirited" driving lol? I've never owned a brand new vehicle before.
Side note: How does engine break in actually work?
Engineering Explained explains it a little in this video and also gives some pointers:
https://m.youtube.com/watch?v=oklqJnm7_TY
Well cars don't need to be broken in like they used to when I was young but I would not drive the car like a lunatic till it had at least 5600 miles on it don't overrap it to the red line and stuff like that and I would change the oil probably the first 3000 Miles and then go to normal
Think of engine break-in in like buying a new pair of leather shoes. At first they're stiff and they don't quite right, but after time they soften up and start to take the shape of your feet.
Similarly, the various metal parts of the engine have never touched before and they need time to bed together on a microscopic level.
But like Scotty said, this has become less important in contemporary cars with modern manufacturing.
Main thing is the rings need to seat against the cylinder walls, especially moly rings. Drive it easy, keep an eye on the oil level and it should be OK.
