Mpg drop after reprogram at the dealer

[Kwitt]

My truck got stuck in 4wd. It would not shift out of 4wd.  I read it was probably a program issue and brought it in to the dealer.  They reprogrammed my truck and it has been fine since.   However before I went in I was averaging 20-22mpg.  Since then I’m averaging 15-17mpg.   Could they have messed with something to cause it to run rich.  I’m thinking if it was programmed for e85 it may cause this????  That was the only change.   Air filters and tires are all good.  

 

My truck is a 2016 Silverado 1500 crew with a 5.3

[wforrest08]

How many miles have you drove it since the reflash? Are you going by the DIC or hand calculating MPGs? Odds are you need to drive it more to get your average back up. Also since it was flashed check to see what the mpg mileage is set to 50, 400, ect. as it probably revered back to whatever the default is as opposed to what you had it set to.

 

There is no factory reflash for E85. There is a sensor in the fuel line that measures the amount of alcohol in the gas and adjust the fuel/air ratio based on that for flex fuel vehicles.

[Kwitt]

10,000 miles.  I have been hand calculating it.  I kept thinking it would get better but it has not.   It was instant after the reprogram.  

 

 

[Grumpy Bear]

These things have adaptive learning capability. When flashed it looses it's previous cumulative 'learned' memory and you start all over again teaching it by the way you drive, the weather, fuel etc. Don't think it ever really quits learning but raw after flash is brutal. Be patient. It does what you tell it to.