Many have responded to you that most GL owner's driving style / commute is the norm and not the exception, as you suggest, so I'll just keep that to a minimum.

I have to point out to others that your last tank, updated 4/29, was 17.5 mpg. You're right, that's horrible mileage. But in the notes section, you stated that this tank was 90% highway driving!!! Perhaps that was a mistake, but if that's true, it's just about impossible--in ANY car of this size, hybrid or not. That's a full 14.5 mpg LOWER than the EPA estimate. You truly have to try VERY hard to achieve that kind of dismal result.

This is again why I try to point out that your particular car, or some combination of your commute and driving style is leading to this result. It is NOT the norm for the GL, and if Saturn was able to produce decent MPG when it was in their hands, there is little left to blame when it comes to the car.