I made it to Florida without the service engine coming on. I kept at 70 mph. Was down to 9 mpg in the mountains of Tenn. up to 10 mpg in Florida. Service engine light came on when I was coming home. Stayed at about 9.5 mpg on way home. I was still in Florida when the light was on and had about 1700 miles on it. I just got home late last night. I drop the Truck off at the Dealer in the morning.