base dc5 gas mileage terrible?

[142763]

Hey,
I currently own a base integra 2005 model and have recently experienced terrible gas mileage. Last year i was getting about 500km - 550km per a tank , now im only getting about 350-400 max per tank?!
There is no engine code that shows up , and i had got it serviced 2 months ago and the mechanic said there were no problems , and proceeded with a full service. spark plugs and everything were changed and there still seems to be a problem.
Now , I'm not thrashing the car or anything , i mean its not even that fast , and use it just to get to point A to point B , and the fuel mileage is killing me . A couple of days ago i filled up a full tank , now today showing 150km its already half way through the gauge. What i alway see happens is one day , the arrow on the fuel gauge will show that its almost half way , then i start up the engine the next day and it will show up higher than it was yesterday. Anyway , i have a obd2 computer thingy that my friend has which i can use , but dont know if it will show any signs. Im thinking a broken o2 sensor but not sure . Will appreciate for help! thanks!

PS i have a K&N CAI , but have had that since the start and was never a problem.

Thanks!

[brenyxus]

So did u solve this problem already? Pls share what's been done to solve it. Thanx in advance

[smiffy]

This may seem obvious, but have you run the tank dry? Could just be your gauge which is faulty.