I Am on a roadtrip from salt lake to california in my '08 silverado with 5.3v8 and active fuel managment. Last time I did this trip under similar conditions I averaged 20mpg. This time my truck feels like it lacks power and I'm averaging 16-17mpg max. It doesn't go into v4 mode as much as it used to. Took to dealer they said everything was fine. I have tried many things myself but havent gotten anywhere. Thanks for any advice or ideas you may have.
