You sure you don't got that backwards??

GT's are 9:4.1

GTP's are 8:5.1 for compression ratio.

And 3.29 final for GT's and 2.93 for GTP's.


Either way they can get the same mpgs within reason if driven the same way. Cost for fuel on a GT will be less than a GTP has they requre 91+ octane. But thats such a small amount.