Here are my
rough averages in my '97 Civic HX with its mostly stock D16Y5 engine...
37mpg = AC-off typical city driving
35mpg = AC-on typical city driving
42mpg = AC-off highway at around 60-75mph
35mpg = AC-on highway at around 60-75mph
30mpg = AC on highway at 80+mph
26mpg = AC-on when I moved from FL to KY with the trunk and back seats loaded up
22mpg = No AC belt when I moved from KY to FL while hauling a half-full 5x8 uHaul trailer, and catching Atlanta traffic.
I've never really tried hyper-miling or eco-driving much more than when I may be running close to empty.
So i just calculated it and i get about 21MPG or 11L/100Km bone stock d16y7
That's just awful for a Civic. You need to seriously address that... in its own thread of course.