My 1st tank was <40 MPG too, then it increased as I got used to "hybrid driving."

As was mentioned earlier, make sure the "ECON" button is lit, otherwise the auto stop will never work. Also make sure you don't take your foot off the brake (even for a split second) after stopping; that will cause the engine to kick in again. Before stopping, coast as much as possible; your MPG will skyrocket and you'll give the IMA a nice charge. Try to keep a constant RPM (more important than constant speed). I've found that ~2000 RPM is the "sweet spot" at 50-60 miles per hour; the MPG graph can go as high as 70 on level ground and 80 on a slight downslope.

You don't mention where you're from, but I can assure you the terrain makes a big difference. Climbing even the shallowest hills will have a negative impact, as will using the A/C (hard to avoid here in Florida). While the difference is far less than it used to be, a manual transmission is still a bit more efficient than an automatic.

Hope this helps. Don't get discouraged.