Are you carrying around a lot of stuff too?I got 36 cold psi. Run 80% highway and changed factory oil out at 1000 miles. I am actually at 5700 miles but started to keep track a little over 3000 miles ago. I changed oil at 5000 miles too. Both times synthetic. Best I have done was 33.52 mpg for a tank, worst was 22.75 mpg.
This with 87 octane top tier gas.
How many people are with you?
Just keep in mind that the more stuff you carry, the lower your MPG will be.
If you don't need to haul it, don't!