***UPDATE***
Having a new truck again has given me the opportunity to drive a whole heck of a lot more, and I love it. Just hit 10,000 mile on the new Tahoe yesterday, having only owned it sor 5 months!
I tried 89 Octane gas from CitGo for about 4 fill ups. I noticed a slight increase in my MPGs and the range on the trip computer on the dash read around 560-610 miles till empty, and that was when I had been doing highway trips w/o traffic between Boston and Long Island. when I'm driving mostly city miles, the range readout drops to 460 on a full tank. So it all has to do with your most recent milage in application to the range computer.
Since I moved back to NY I've switched back to 87 because of the price difference. its a whole heaping 1.20-1.50 $ more per gallon here on the island than most other places I found in New England.
In terms of MPGs, its a whole heck of a lot better than my old 2002 Tahoe. The old one had a 4.8 Vortec and it got a maximum (without A/C or Heat running) 17 MPG highway and that was down wind downhill.
I just took a trip yesterday from Patchogue to Southampton about an 80-100 mile round trip and had a 25.5 mpg average with cruse control set at 65 mph both ways. The best average I've gotten so far is 29.8 MPG and when I'm doing mostly city driving it dips down to 17 mpg. I think I could have gotten even better milage yesterday if I hadn't throttled it from 65-110 mph for a few seconds on the straights, but where's the fun in that.
Overall I'm thoroughly impressed by this car and its efficiency as well as its sporty-ness. I'm still waiting to try it out in the snow this winter, I hope its as good if not better than my old one.
Blessing and God's grace to you all, thank you for all of your help and support in my new truck endeavors!
