I bought my 2011 Patriot on December 20, 2010, in large part because of the advertised gas mileage. The window sticker for my 2.4L, CVTII, 4WD is 21 mpg city and 26 mpg highway. Thus far, while driving in very light city conditions and then on a highway trip to Pittsburgh (from Erie, PA), I have been getting 17-18 mpg and 21-22 mpg, respectively. That is far below the advertised mileage, and that's with only a couple miles of 4WD driving time, and I do not let the vehicle sit idling at ATMs nor do I let it idle a long to warm up (kept in a partially heated garage). On my last vehicle (2007 Cobalt) I routinely beat the sticker mpg by 5-7 mpg, so my driving habits are not at fault.
When I called the dealer's service department (Gary Miller Chrysler-Jeep. Erie, PA), I was told it's because of winter fuel mixture, the engine not being broken in yet, and even that the fan motor from the heater are the cause. The guy was serious about the fan motor on the heater. The EPA is very stringent about the conditions under which mileage ratings are published, so I don't buy the line. Modern engines are built to very close tolerances and require almost no break-in period. The winter fuel blend might be responsible for a little of the bad mileage, but this is 20% below advertised. It's at the very bottom of the range that factors in worst-case conditions like full load of passengers and cargo, hilly terrain, windows down, etc. My conditions are about as close to ideal as possible.
With gas heading for $4 per gallon, this is very distressing. I specifically chose the Patriot over the Ford Escape because of the gas mileage. My 4-cylinder Patriot is getting the gas mileage of the 6-cylinder Escape - totally unacceptable. BTW, mileage calculations are via the Vehicle Information Center (VIC) computer that I ordered with it, so the values are not subject to filling at the same gas pump each time, tracking miles accurately, etc; the VIC calculates the values real-time, and I monitor them closely.
For the first-ever Chrysler product in my 52 years, I'm not impressed.