Fuel Efficiency decrease

[glentutz_99G]

I did some tune up for my car yesterday. Ireplaced my spark plugs with a Denso Iridium. Bought a new PCV valve. Changed my oil. Today, I replaced my air filter with a K&N one. My problem is, since yesterday after fill up, my gas tank is almost half empty. I can't seem to figure out what. I've been searching online and hasn't really found anything. haven't checked my O2 sensor as I don't know where it's at. I still have to look for it. I have a 99 Galant DE. How about the fuel filter? could it be the culprit?

[pinoyesv6]

so things got worse after you did the upgrades or even before it?

[DOHCstunr]

is it possible that you've been getting on it alot since the new parts?

some mods will allow your engine to feel less restriction and hence give you better mileage. but if you are getting on it the extra air will be given more fuel. and your mileagee will be worse than before.

[glentutz_99G]

before a tankful used to last me 2 weeks. that's about 10 miles one way to work. yesterday i only did a couple of trips to and from my work and a trip to the store to get the parts which i assume is about 6 miles one way. anyway, with the K&N filter i can feel the extra air coming in.it breathes a lot better and i don't feel much restriction and throttle is a lot more responsive. i'm trying to make my car as fuel efficient as i can because next week i'm starting on my driving trip from vacaville, ca to anchorage, alaska so i can leave my car with my sister before i move to Germany for an assignment. do u think it could be because of the new parts? or maybe the O2 sensor or fuel filter? i have 63997 miles on it. bought it with an aftermarket exhaust tail pipe and a front bumper kit which i since damaged and replaced with stock.

[pLUGSNEt]

Hmm thats kind of od... I drive 47.1 miles one way to work every day I have a intake and aftermarket exhaust.... plus 20inch rims and I fill up sunday night full to the T... 13.6 gallons or whatever by friday morning im ready to fill up again.. I say a full tank last me about 400+ miles thats pretty much work home work home.. no extra driving.. all on the highway but alot of times the high way is backed up on the i20 going home... so that stop and go traffic pretty much.... And I hate my mpg rite now...

Hence that is why im buying a stick shift civic in a month or so to cut down on gas....

I know for a fact my intake makes me waist more gas... because i remember after i had put it on.. LOL my gas would sink like a rock compared to before.... the dubz really didnt put a dent in my gas mileage.... I am personally wanting to go back with stock intake but i like the look of aftermarket intake.. if i get this civic i wont have to worry bout it but I know I need to get a tune up LOL...