i average between 22-25 mpg on the 02 gt 5-spd, with about 3/4 highway driving. The EPA city rating is 15-16, but you can exceed that pretty easily if you don't get on it very often.
2002 Mustang GT: 5-spd, 96k: CAI, IAC restrictor plate, Mac Prochamber O/R, Borla Stingers
268 rwhp / 312 lb-ft
2015 Chevy Colorado 4cyl, 6-spd manual
1972 Yamaha CT2 175cc