I don't know for sure. I thought the FE testing procedure was the same. Just the PCM/ECM(?) software was adjusted from 2005 to 2006. But the current update was supposed to revert back to the 2005 values? I could be way off on this. If fact, I hope I'm way off on this. It would be nice to see a 2 mpg improvement in my current FE.

However, the thing that I did hear which changed in their testing procedure was in how they rated horsepower. The 2006 is supposed to be the same horsepower as the 2005. But the 2006 is rated at 253 hp whereas the 2005 is rated at 255 hp. Mechanically, there's no difference between both years, just that the SAE testing procedures changed.

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