Hmmmm... From the Car and Driver article.
"The 4140-pound 300C Hemi scores 17 mpg in city driving and 25 on the highway in EPA tests. The
Car and Driver test, admittedly riotous, resulted in 17 miles to the gallon."
Found here...
http://www.caranddriver.com/article.asp?section_id=3&article_id=8009&page_numb er=1
From 10.5 to 17, thats a huge difference.