But you should be aware that in 2011, the CAFE standards change for trucks, as they will be defined based on "footprint" - so next year, the GVWR of 8500 lbs as the break point between light and medium duty is out the window, and many of the 2500/3500 series vehicles will come into play for the CAFE standards.
Howna00 is correct that there is a big difference difference between CAFE and EPA estimates (a very ballpark figure is that EPA is about 80% of CAFE). The flex fuel calculations look promising, and even through mathematically they could really jack the numbers up, they cannot show an increase greater than 1.2 mpg. Probably a good thing since E85 is still pretty scarce.
And to add one more complicating factor vis a vis CAFE, you have to remember it is a harmonic mean, not an arithmetic mean for the fleet. In other words, this is a measure of fuel efficiency AND production numbers. This is why fleet sales are so critical to manufacturers to meeting CAFE standards, as they can jack their production up on smaller fuel efficient vehicles to meet projected fleet sales. This effectively skews the CAFE averages up, so there is less criticality to improving things like fuel economy on medium duty trucks since the volume will be so much lower.
Jim
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