[drivemusicnow]

I guess I'll be the one to disagree.

There is NO reason on a modern engine that was built to spec to "go easy" for a while.

EVERY motor built in a factory of any quality is flogged on a dyno, or in the car on a track before it is ever delivered. Why you ask?

Think of it this way. If something was done wrong (For example to tight of clearances, or too loose torque on bolts etc) it won't fix itself and will eventually fail, even if you spend the first 1000 miles driving like a blind grandmother.

My recomendation, and that of many other people who build numerous modern engines, is to:
Vary RPMs constantly
Do some "not quite full" throttle pulls, and then while holding it in that same gear, let the engine act as a brake

Change the oil after the initial break in. This includes letting the car idle until warm, lots of various RPM and loads, and less than 50 miles.

If something was done wrong, it will fail. If everything was built right, it'll have higher compression, and last longer than the same motor that was broken in "soft".

Many of the rules behind engine break in come from old engines with much looser machining tolerances than are available today.

Google the "mototune" break in method. The same idea is used by factories all over the world, as well as EVERY race engine builder in the world.

Some people will say, "oh well that's fine, but a race engine isn't trying to last 100k miles" which is true, but you have to think that they're also looking for every last hp, and an efficient motor (read high output) is a low wear engine, assuming that the motor in general was designed correctly.

Even so, most people are stuck on the "take it easy" break in method for the mere reason that they just spent a significant amount of money and in their minds they think being "nice" to it during break in will make it last longer.