Most people are getting more like 15-20 but I say a lot depends on your driving habits.
If you short trip a lot that hurts mpg. I've only seen it on diesels but I think it can happen on gassers too. If you drive a couple miles at a time your engine is much less efficient while its warming up.
Around town only, which are short stop/go trips, I get 11mpg from a 2015 5.7 4x4. Which is about what I was expecting. Haven't had it long enough to do a freeway trip yet.
Since you have less than 10k miles in about 1.5 year span. I will say your mpg is "normal". I'm guessing your trips are less than 10 mins in city driving.
Maybe idling more than others too.
I had 4 minute commute. Killed my calculated mpg, but a tank will last me 3 weeks.
2012 JGC 4x4 w/5.7 hemi with 40,500 miles and driven most of the time on the highway. Last 15 tanks I've used 89 octane and averaged 19.84 mpg. Really pleased with this and I only had 18.4 mpg when I was using 87 octane. Can't and won't complain.
I get about 12 mpg in my 2012 Overland Summit 5.7 Hemi. But, I also drive a little more aggressive than most JGC probably owners do. I do probably half and half city/hwy.