Good morning
,
Granted, this is only one data point, but I believe my engine in my 2008 Civic Si sedan is starting to break in. I had a tank of 38.18 mpg yesterday on a ride to my home office in CT. Overall, my average is just over 35mpg for the 3400 miles I've got on the car, but things are starting to move along. Prior to the trip to CT, I changed the oil for the first time. Since it's still breaking in, I went with regular old Pennzoil 5w30. I'll probably put synthetic in once the temperatures get a little colder.
Thanks,
Bogatyr