I just returned from a trip to the Milwaukee Hybrid Group so took a few notes along the way to post for this thread. Boy what differences in price. I especially liked the 10-cent to 20-cent change inside of 15 miles around the North Chicago, IL area.

Min price was $2.09 near Gurnee, IL on the way out and I saw that same price near the Prime Outlet shops in Fremont, IN on the way back.

Max price was $2.36 in Oak Creek, WI (which beat out the $2.34 price on the Indiana Turnpike even!).

$2.18 @ I-79 near Pittsburgh, PA
$2.19 @ I-80/I-90 near Sheffield, OH
$2.18 @ I-80 near Toledo, OH
$2.24 @ I-80 at last Westbound service plaza in OH
$2.34 @ I-80 at first Westbound service plaza near Angola, IN
$2.15 @ I-80/I-90 near Portage, IN
$2.21 @ I-94 near Highland Park, IL
$2.29 @ I-94 near North Chicago, IL (~10 miles from Highland Park, IL)
$2.09 @ I-94 near Gurnee, IL (~5 miles from North Chicago, IL)
$2.36 @ I-94 near Oak Creek, WI
$2.25 @ I-94 near Delafield, WI
$2.12 @ I-80 near Fremont, IN
$2.16 @ Rt 20 near Angola, IN (~8 miles from Fremont, IN but off the turnpike)
$2.18 @ I-79 near Pittsburgh, PA

--> Averaged 685 miles/week and 49.0 mpg in first year (35.7k miles from Aug 7, 2006 to Aug 7, 2007)