Apparently the company switched its name to the acronym in 1991, according to Wikipedia. Stores made in the 80's would retain the signs saying "Kentucky Fried Chicken" while all newer stores would use the new "KFC" logo.
Posted under General
Amusingly, an acronym has not stopped people from calling it by its original full name.
With the addition of jjj14's comment. Should it go back to KFC and alias the full name to the acronym? There are only three tags (this one), the yu artist and another artist under these letters.