Now that I confirmed Fuel-Cut in my '09 FEH, I've been taking advantage of it more and I can see the results between the Nav sys average MPG go even lower than both SGII averages. I reset the SGII's with my first fill-up at 592.6 miles and my SG's showed an average of 46.4mpg and my Nav average was 44.3mpg, which was 2.1mpg lower. Since that time, I've used more fuel-cut techniques on average and can see a bigger difference in just 133.7 miles after the reset of all three Gauges. Now my SG's are reading 48.7mpg Tank averages and the Nav sys is reading a 46.4mpg, a 2.5mpg average lower than my SGII's.

One good thing that Ford changed in the new Nav sys was they increase the data memory so that the data does not drop off before an entire tank is used. My '05 FEH loses data after a little over 200 miles after a reset. The 40 Gig Map system and the 10 Gig song and picture system must have allowed Ford to increase the MPG average data also.