don't feel too discouraged!

The cold will reduce gas mileage; ethanol has less energy than typical gasoline.

I achieved 30 MPG rolling along at about 60-65 miles per hour (try to maintain 100 km/h) for about 6 hours. 10-mile legs might not be enough to warm up the engine much.

Just take it easy during the break-in period and enjoy the car. It seems larger to me than a 4runner. I think it's a great vehicle. You won't see a payback in reduced gas consumption versus a non-hybrid Highlander. But I think it's the nicest passenger vehicle that Toyota makes right now (built in the Lexus LX350 factory, I think).