OK, following everyone's advice I checked the tire pressure. It was at just 30 psi. I increased that to 45 psi. I drove just under our 70 miles per hour limit for a 100 mile trip today. My average jumped from 35.4 to 44.8 miles per hour! Great advice everyone. Thanks.

Congratulations on the increased mileage!

One thing I would point out is that if you make that same trip, with your speed at 65 miles per hour or just under, you will easily top 50 mpg; possibly near to 55, with your tired juiced at 45 psi. My tires are at about 37, and I get about 52 mpg at 65 miles per hour.

I'm not telling you this to try to coerce your speed habits or anything. Your preferred speed may not be that low, or you may be driving on an interstate with a speed limit of 75, or whatever. I'm just letting you know that if you ever choose to experiment in that way, you will probably top 50 mpg for the trip. That's been my experience, and my HCH-owning colleagues here at work.

Enjoy your great car!