The 2012 owners manual states:
"We do not recommend taking fuel economy measurements during the first 1,000 miles (1,600 km) of driving (engine break-in period). You will get a more accurate measurement after 2,000 miles–3,000 miles (3,000 km–5,000 km).
Guessing the 2013 would be similar but too lazy to verify...anyways, My experience was:
0-1000: low-mid 20's
1-2000: improved to just under 30
2-3000: improved to low 30's
3-4000+: low/mid 30's in mixed driving, finally seeing 39~42 on the highway
When I hit the 1,000 mile mark, the change occurred between fill-ups...
998, 999, 1000 >>Ding - Level Up! - 5mpg fuel economy upgrade unlocked
Subsequent improvements were also noticeable, but much more gradual.
I did a LOT of highway driving, which may or may not have something to do with the slightly longer break-in.
Also, it seems theres a slight power increase as the engine breaks in.
Give it some time and the occasional full throttle run, it'll break-in nicely.
As a side note, a few folks have noted the 18" wheels cost a few mpg as compared to the 15-17" wheels...YMMV