Here is a test that I have done time and time again so this is accurate on my truck.
These are the readings I logged with the canned Gryph 87 tow tune:
message center = 12.0 mpg's
Gryphon = 14.5mpg's
So when it states 12.0mpg's it is really 10.7 using "good-o'l-fashion" tools, pen n paper. The message center on my pickup is off by -1.3 mpg's and as for the gryphon, I could not count that high.
2007 F150 SCrew
stock 4x4