my gli 2007 is doing +- 100 with ac on cng in local with 50 cylinder since 2007 when i bought it and converted to cng

is it good milage? cuz i've seen gli's doing 170 plus on cng with ac on local with same 50 cylinder

someone told me my gli's milage is not good and it needs checking from a good mechanic for cng.

plus i've seen city 2007 doing 150 plus milage with same specs

pls comment and adivce