Hi I am having an issue with my gas mileage lately, I am currently averaging 12.9 mpg. Any ideas of what could be responsible for the diminished mileage? Oil and filter changed every 3500 miles, performance air filter (recently cleaned).

 

That's on par with what I get city, bolt ons including test pipes.

 

maybe try resetting your ECU.

 

What was it before? Usually a heavy drop in mpg points to a bad O2 sensor, and it wouldn't hurt to clean your MAF sensor.

 

O2 sensors are about a year old and I cleaned the MAF sensor around the same time. I reset the ECU about 4 months ago, mods are minimal at the moment, intake and exhaust currently engine wise, everything else is exterior. I am going to change out the spark plugs this week as they haven't been changed before and will check vac and fuel lines for fuel leaks, I do get a fuel sent outside the care time to time. It has been declining since I was rear ended, I'm starting to think there is a crack in the fuel filler hose and sometimes I can't fill the tank all the way because it keep overflowing early so I'm guessing there is an issue with the filler hose. Thanks for the comments, any other ideas would be appreciated as well!

 

If you smell gas all the time that isn't something you should wait to get checked.