Okay. I can understand why it's important to break-in the engine by varying speeds. But what would happen to the engine if we didn't do this? Will anything break?

Also if we had to drive constant freeway speeds for a while, can't we just extend the break-in period longer prior to exceeding the 4500 rpm and 100 mph to achieve the same affects?

A lot of these concepts are so different from what was instructed to us years ago with older cars. ie: I was always told to let the car idle for about 30 seconds if the car's engine is cold (in the mornings) to let the fuel mix and lubricate, then drive slowly until normal temperature is reached.

I'm just wondering if technology has changed or if I was just doing things wrong previously.