Just picked up a 2008 HiHy Limited. Love it so far. Normal driving we are getting about 28-29mpg, mixed city and highway. I am pretty sure as we learn to drive it we get at least 33mpg out of it. My question is for those who have a HiHy what tire pressure are you running?
I have an 08 also - only about 1600 miles on it so far, not as great mileage as you are getting, avg is 27. I've been experimenting with the air pressure. I'm running about 90% of the sidewall printed maximum right now in the front and rear since I have the 4x4. It didn't change the ride much at all - least I can't tell that it did. With that (around 38psi), it runs up well over 42 to 44psi when hot (ignore the tire sensors - they are extremely inaccurate - use a good digital.) Haven't noticed much difference in mpg yet - if I ever will. the temp climbed up here radically (northern virginia) which forces me to use the A/C and that drops the mpg to 25 so not sure I will be able to quantify results. At this weight - I would only suggest that you run the tires firm, but don't overinflate.
We have the Michelin Energy (?LX4?) tires on our HiHy and I keep them at 35psi...it's my wife's daily driver and I don't think she really wants me 'playing' too much with higher pressures.