Did a Road trip this weekend from VT to NJ (about 600 miles round trip). About 50 miles of the trip is Country Highway (50mph or 55mph) and the rest is 65mph 4+ lane highway. I had my snow tires still on (made the call today: I'm done with Winter - they're off now!), the roof rack was off, and there was myself and my son heading down to the NY Auto Show (Packed for 4 days - so not a lot of stuff). I averaged about 75mph on the highway heading down to NJ and about 55mph on the country roads. Calculated economy was around 31.5mpg. Coming back up, it was around 33mpg with essentially the same relative speeds (I'd guess I was moving a little quicker on the way home though).

Heading down, I had a little bit of a headwind whereas on the return, it was hitting me from the side - not fun with the snow tires. Also was running on VT Fuel on the way down vs. NJ Fuel on the way back up - not sure the ethanol differences.

The week before, I was running around the state of VT on country roads and averaged 34mpg (again snow tires and VT Fuel). I Just swapped over to the summer tires (Hankook UHP All Seasons) and we'll see what the differences are there.

The 30-32mpg seems about right for the OP's claims compared to my trip this weekend.

~SB