Hyundai Repair: high fuei consumption on Sonata 2006 2.4 A/t, powertrain control module, poor fuel economy

Question
I hv done 13000km on my Sonata 2006 2.4 a/t.  The problem is that i find fuel consumption in the city very high. On the high ways it is ok but in the city i get now 16.0liter / 100km. Infact recently it has gone even higher bcz one month back i was doing 13 - 13.5 litre / 100km in the city. Could you give me possible cause of high fuel consumption. I hv checked on various forums and everyone give consumpiton between 9.0 - 12.00 litre / 100km but mine is very high by all comparisons. Will appreciate your possible cause and remedy check list. thanks

Answer
Since I'm fairly ignorant regarding fuel economy measures that aren't in U.S.  units, the first thing I did here was to convert these to U.S. values and compare to the U.S.
EPA ratings.  In U.S. figures, your fuel economy is 14.7 miles per gallon (MPG), while the EPA rating is 21 MPG.  U.S. EPA ratings can be found at www.fueleconomy.gov.  I'll agree that this is low enough to cause concern.  The numbers you report seeing translate to 20 to 26 MPG.  This is on the high end of the spectrum for city driving.  I'd expect more in the range of 18 - 22 (11 - 13 L/100km).

The problem, however, is that many factors affect fuel consumption, including fuel mixtures, which vary from place to place.  Realistically speaking, poor fuel economy is typically a symptom of a problem that may or may not have other consequences.  First, you'll want to ensure that your engine and transmission seem to be operating properly.  Does your engine have the proper amount of power?  Is your check engine lamp off?  Does the transmission shift through all four forward gears properly?  Does the torque converter clutch engage when requested?  Just about any problem that negatively affects engine or transmission performance will negatively affect fuel economy.  Ideally, you'll want to have this checked with a scan tool.  This will allow checking for trouble codes as well as monitoring all the data from the powertrain control module (PCM) to be sure it's normal.

You should also check things that may prevent the vehicle from rolling easily.  Do the brakes stay partially applied?  Is the wheel alignment within specification?  Are the tires inflated to at least the recommended pressure?

And you'll also need to examine your driving situations and habits.  The longer you sit idle, the more fuel you'll use.  The more you accelerate and the harder you accelerate, the more fuel you'll use.  And the more you apply the brakes, the more fuel you'll use (because you must have accelerated to need to apply the brakes).  

Most of all, keep an open mind.  If you sit idle too large a percentage of your driving time, this may be the best fuel economy you'll achieve.  On the other hand,  if you can locate a problem with the vehicle or a way to drive more economically, you should be able to improve your fuel economy.