Chevrolet estimates the fuel mileage at 32 mpg for highway use. I am averaging 21 mpg highway use. I questioned the Chevrolet dealership if they good make some adjustment to increase the mileage and I was told if there were no warning lights on that everything was performing properly. It would be interesting to see how GM comes up with their numbers. It certainly isn't real world data. Most of my driving is highway and normal speed limits with air conditioning on, no mountains.