Time for a NEW car!!
The secret....
2013/2014 V6 Mustang with the V6 Performance Package ($1995 Option).
Under $25,000 (MSRP). 30 MPG. Should get you into the mid 13s with little effort.
Next would be the Challenger R/T
The Camaro isn't something I would own for many reasons, #1 being visibility.