I bought a 2004 Civic EX Automatic last week, my first ever brand new car. Admittedly, I'm very lacking in car engine knowledge, and I was unaware of the "breakin period" until I came across it in the manual today. I already went about 300 miles, and though I'm pretty gentle in general, I've definitely revved to 3500/4500rpm more than a few times, though I haven't floored it or done any hard braking. What kind of problems could this cause? I've been reading things that say the breakin period is definitely important, and some that say it's completely unnecessary.