am surprised still did u try a different petrol station ?
try shell marine drive clifton and let us know if any improvement.
even the honda guys say no tuneup needed because it is electronically adjusted so even if any issues like choked air filter the oxygen sensor works to adjust the fuel ratio automatically.
still you should get max 8.5 avg with AC.
Are you getting 7.5 with AC 100% on or... ?
Did you use LX treatment to improve fuel combustion % ?