Congratulations on your new Civic, I too have a 2008 Honda Civic EX AT sedan, and beside the obvious "no-no's" such as abrupt acceleration and harsh braking, I've also heard not to exceed speeds of 55 mph for the first 1000 miles, but that could just be an urban myth kind of thing that I still chose to practice. All of the break-in period procedures should be in the manual. Oh, and as far as the 10k mile oil changes, those are just estimates and being that your Civic is equipped with Honda's "maintenace minder system", it will inform you of the life of your oil and other key components based on how you drive and the conditions your vehicle undergoes which eliminates the guess work involved in maintaining your vehicle.....So you've gotten 38.26 mpg so far, that's amazing, because so far I've only been able to get 29 mpg mixed driving and that's because I consider myself somewhat of a "hypermiler" (I cruise at 60 mph on the highway and all shifts are at 2K rpm or below except for when the rare occasion of merging/passing arises and glide as much as possible). Once again congrats with your new Civic and a quick question, does your engine vibrate? Mine didn't vibrate at all until I hit around 800 miles (I now have about 2,200 miles) which continues to aggrivate me because engine vibration at idle is one of my biggest pet peeves.