Look for gasoline leak at fuel injectors. You can usually smell it. If no leak change air filter. A plugged air filter can cause too rich mixture and too much gas usage. Also inspect gasline from tank to gas filter and around filter.
The 2003 Nissan Altima is a gas-powered vehicle.
The 2012 Nissan Altima is a gas-powered vehicle.
The 2007 Nissan Altima is a gas-powered vehicle.
The 2005 Nissan Altima is a gas-powered vehicle.
The 2011 Nissan Altima is a gas-powered vehicle.
The 2014 Nissan Altima is a gas-powered vehicle.
The 2008 Nissan Altima is a gas-powered vehicle.
The 2010 Nissan Altima is a gas-powered vehicle.
The 2002 Nissan Altima is a gas-powered vehicle.
The 2004 Nissan Altima is a gas-powered vehicle.
The 2001 Nissan Altima is a gas-powered vehicle.
The 2006 Nissan Altima is a gas-powered vehicle.