Nissan Repair: Gas milage, nissan sentra ser spec v, mass airflow sensor

Question
I have a 2004 nissan sentra ser spec v 2.5 and I have been getting 15.8 mpg city I have changed air filter spark plugs pcv valve I had a fuel system clean out and put injector and premium fuel I have no idea what it could be any solutions)?Thnx

Answer
Josh,

I would first ask if the check engine light is on?  If it is go to Autozone or Checker and get the code read for free.  Email me back the code or codes they give you and we'll go from there.  Now, from my experience with Sentra's it is usually the mass airflow sensor that has failed or the converter on the exhaust has started to melt and plug.