I have a 1LT automatic with the RS package, at those speed on the highway I get 36-42mpg(pretty much the same). Might want to try premium a few tanks, most have seen a 2-4mpg increase. I only see the difference on mostly highway driving so the way you drive you might also see an increase.I commute about 150 to 200 miles a day for work and drive about 70% highway. My commute takes me from Pennsylvania to central and northern New jersey with rolling hills. To date I am averaging between 39 and 41 MPG consistently on each trip. I use 87 octane, drive between 65 and 68 mph on cruise whenever I can.