I know its not a Compass, but its the same drivetrain. My Caliber R/T FWD averaged 28 or 27.8 (whichever you prefer, I rounded up) on my first tank today. That's with liberal use of Autostick and cruise control though. Plus, I dont think I have as much ground clearance. Might be helpful, not sure guys.
1998 TJ Wrangler SE - Stone White, 2.5Ls of screaming lifter clacking power, AX5, 31" BFGoodrich All Terrain T/A KOs
2010 Wrangler Unlimited Sahara - Deep Water Blue, 3.8Ls of oil consuming fury, NSG-370, BFGoodrich Rugged Terrain T/A 265/70/R18s