So I noticed on my last 3 or 4 tanks of fuel, I seem to be getting only 190 miles out of a full tank. When it was brand new, I got roughly 240 a tank. It has a K&N drop in, for less than 5k miles, the oil was changed maybe 2k miles ago. I checked the air filter today, checked to see if some jealous **** had something shoved in my exhaust, and checked my oil. I have no idea what's going on. Any ideas?

 

get a tune.. the k&n can cause problems without it

 

It's just an OEM type drop in filter, not a cone or anything, the stock airbox is intact, it just flows a little better. I thought it didn't need a tune until you go for the full intake kit, etc...

Am I wrong?

 

You should still get a tune, but check your O2 sensors. I was only getting 10 mpg. I fixed the rear O2 sensor and im getting the best gas mileage ive ever had. If you dont want to replace it you can basically flash the O2 senor out of the picture which is what i did.

 

how many miles on it? a bad 02 sensor will rob gas mileage/are you in boost all the time?

 

boost leak??????????????????????

 

Low tire pressure?

 

Boost leak +2

 

..........

 

Have you been boost a lot lately??

If not, check tire pressure.

 

tire pressure would not affect gas milage that much it's either
mass air,plugs,or boost leak.....

 

Tire pressure will effect it a lot, I've seen people come in saying bad gas milage and have all 4 tires at like 20psi or a few at 15. That will increase rolling resistance a lot and if you do highway driving it will wear your tires more and decrease gas milage significantly.

 

Tires under-inflated by 15% will cause fuel penalties of around 2.5%, and a 30% under-inflation will increase fuel consumption by 5%.

 

I think it's you....not the car. You got heavy foot, smash on the gas pedal too much.

 

Brand new Direzza's, 2 weeks old, balanced, inflated, and alignment done. Brand new plugs, 2 months old.

I have just under 13k miles on it.

I don't have a problem boosting, but I'm not always in the boost either.

I did an oil change today, also cleaned, re-oiled the air filter, used an octane booster/fuel treatment, just to be on the safe side and do the easy, DIY things I could think of.

If it's a bad O2 sensor, how do I get that checked short of taking it to a dealership, is it something I can DIY?

haha, I thought that myself at first, so the next two tanks of fuel, I drove extra slow, and extra careful. And... tada ~10mpg!