Hi Suze, No, Kansas isn't a mysterous sinkhole. It is on the Great Plains, though, so if you are fuel smart, you need to take the wind direction into account. Smart Cars are really susceptible to wind affecting mpg. Wind resistance becomes a factor about 35 mph and half your horsepower (gasoline) is used to push wind aside at 65-70 mph.
If you are driving into a 20 mph headwind, you will get the same mpg at 45 mph that you got at 65 mph without the headwind. That's the bad news.
The good news is that with a tailwind, you'll get your best mileage.
If you want to boost your mileage even further, the Smart Car has great downhill coasting ability. Return to high gear by keeping your foot completely off the gas pedal, shift to Drive (D) with the stick and immediately, in one smooth motion (you have one second to beat the computer), slide over to manual and forward into high (5). This avoids sometimes dropping into 4th with the new transmission shifting update.
The other big trick is to use the Constant Throttle Technique. Find the throttle position for your chosen cruising speed (keeping in mind that slower speeds give better mileage) and hold it absolutely steady, regardless of terrain. Simply allow your transmission to shift normally in automatic mode.
I have learned to detect a subtle, deep throb where the Smart Car gets its best fuel mileage. You can easily find it in 5th gear at 45 mph by applying the throttle very slowly and listening for the change. By recognizing this throb, you can beat the mileage of the auto shift by shifting manually to stay in this range.
I have to drive in my socks to get my best mileage. Even tennis shoes make my right foot too insensitive to hold the throttle perfectly steady. I don't know anybody else who does this.
Also, avoid mandated ethanol areas when travelling on long trips. Ethanol robs mileage. Most of these areas are near big cities but the 10% mixture is becoming more common. In Kansas, it is possible to make a big mistake by fueling with an orange pump handle. Orange pumps provide ethanol mixtures of 20% (E20), 30% (E30), 50% (E50) or 85% (E85). You didn't do that, did you?
Ptero
Lifetime average without towing: 52 mpg