Nissan Repair: Nissan Sentra gas mileage, nissan sentra, k n air filter

Question
I have a Nissan Sentra (2004) that is only getting about 28-29 mpg mixed and it is rated for 28 city 35 hwy.  I have read where many people are getting 33  mpg with their Sentra.  What  do you think can be done to increase the gas mileage?

Answer
PJ,

Good gas as in premium to allow the computer to advance the timing as far as possible.  A K&N air filter and a free flowing exhaust like Magnaflow or the like.  Also, make sure the tires are full of air and you are not hauling around heavy things in the trunk.