Originally Posted by Big John Sny
I don't know how this affects your results, but the fuel here in Dallas and many other large metropolitan areas in the US has changed quite a bit in recent years. I am getting significantly lower fuel milage numbers in all of my vehicles. Any additives they add will add volume of fuel without adding energy (some of these additives are seasonal). The addition of ethanol adds less energy per equivilant volume of gasoline it is replacing.
I was getting a consistant 31mpg till I moved the needles back to the factory setting and started getting 35. I would really love to get 40, but my car that used to get 34 is now getting 30 and my minivan that was getting 25 is now getting 20 (both get slightly better when I get gas outside the metroplex), so I don't see that happening. I have used my wifes 250 ninja to go to work that should be getting 65 and I get just over 50, so maybe it is just me (although my wife says both cars get 2 mpg better when I drive them than when she does).
Next time you are filling up instigate that pump and let us know how much ethanol your fuel has. That is one bad additive which will scalp your fuel economy. Gallon for gallon, ethanol has about 25% less potential energy than straight gasoline.