My '79 Mustang had a turbo 4, 19mpg. Blew it up, put in a non-turbo 4, 19 mpg. Chucked it for a '69 hipo 351 Windsor and 4-over std., 19 mpg!
These are Canadian gallons,by the way.
Fords are pre-programmed to get less than 20 mpg.