Not knowing much about engines at what mileage should you push your engine to the max on a straight stretch of highway!!!

The standard break-in is 500 miles, so take it easy until then, don't run the engine at a constant rpm ( long highway runs are not a good idea without varying the speed every few minutes ). I waited until ca. 1000 miles before I got medieval on it. Enjoy!

Then again there are those that say "break it in according to how you will use it." If you gonna cruise it, then break it in slowly; if you gonna get medevil, then punch the you know what out of it. I've always followed the lattter of the two choices(punch it) and never had a problem. Supposedly it has to do with seating the valves. I could be crazy though.

"Those who say" to drive the s**t out of it are repeating an old wive's tale, urban legend - whatever you want to call it. The fact is that production engines require some time to wear in tight fitting parts, and avoiding this step can cause damage. The extent depends on the production tolerences of the parts, which due to the ganging of tolerences can cause galling or worse. Or you may never notice the damage if it is slight. There is no downside to following the recommended breakin procedure, but there ARE downsides to driving it too hard initially. No, wait, there is a downside - impatient drivers can't wait, not being familiar with delayed gratification. A sad character fault...

Expensive racing engines don't require an extensive break in because they are assemnbled to very tightly controlled tolerences, so time is not required for tight fitting parts to wear in together. Our "cheap" production engines are not so lucky.