2010 Chevy Avalanche 5.3L Flex Fuel 87 Econ tune

[Sensei Craig]

Hi All,
I searched but did not find a topic on my question.
I installed the 87 economy tune and saw a drop in fuel economny of a full 1 MPG.
I was getting 18.6 MPG highway with base OEM cal.
I put in the Diablo 87 economy tune with tire diameter change only and lost a full MPG over 500 miles.
I have gone back and forth now twice, same delta.
Any thoughts?
I do have the latest version install on my unit.
Confused in NY.

[mikel]

are you saying you calibrated the speedo at the same time you loaded the tune?
if so, whatever you were seeing before the speedo was calibrated was incorrect....now that you corrected speedo you are seeing real data...

[Pastorchico]

What custom setting did you use if I may ask.