I got it done at Honda dealer in Silicon Valley (Can I name the dealership?)

After 300 miles, my mileage is better than average (48mpg - 50miles into tank).

Maybe, draining oil and refilling leave some spots that doesn't get lubricated for awhile?

Here is my observation:
6 miles - 8400 miles -- 44-45mpg
~8200 - 8400 miles -- 46mpg
~8400-8650 miles -- 41mpg
8650 - 8700 miles -- 48mpg..

Interesting....

BTW, I will be making a road trip to Long Beach, CA from San Jose next week.
I'll report afterwards.

John