Average, city, or highway?

If average, depending on what your mpg was before, 2 mpg is a 6-8% increase in fuel economy. For a simple software change that's quite a significant improvement. In addition, any improvement is likely to have most effect on city fuel economyand I believe that the numbers I quoted for the fuel economy of the 07 HAH bear this out.

Nevertheless, it does seem that my highway fuel economy has improved by 1-2 mpg since the update.