I have a 15 Chevy High Country w/ 6.2 L, after 12,000 miles my average mpg shows 16.6. Best was 22mpg on the interstate at 80mph. Only thing i don't care for is that 8 speed auto doesn't know what gear to be in when you slow down in town. And i get better mileage than me wifes Terrian that has a...