Any vehicle that can run on E85 (85 percent ethanol, 15 percent gasoline) gets to average the fuel economy when operating on gasoline with the fuel economy running on the flex fuel, but the latter calculation counts only the gasoline content (15 percent), which has the effect of multiplying that fuel economy by 6.67. Let's look at the example of a flex-fuel Crown Vic:
Average combined fuel economy on gasoline: 24.1 mpg (uncorrected)
Average combined fuel economy on E85: 17.6 mpg/0.15 = 117.2 mpg
CAFE figure: 1/(0.5/24.1 + 0.5/117.2) = 40 mpg
For convenience, this same 15 percent (6.67x multiplier) is used for gallon-equivalent values of other flex fuels like natural gas, even on dedicated natural-gas vehicles like the
Civic GX (100 cubic feet of natural gas = 0.823 gallon of gasoline equivalent):
Average combined fuel economy: 37.5 mpg (equivalent) / 0.15 = 250.1 mpg
The caveat: The combined effect of such alternate-fuel vehicles on a company's overall sales-weighted CAFE can be no more than 1.2 mpg for the next few years, and then it will phase out under a schedule shown below. The Greenhouse Gas folks, however, are contemplating extending the credit if manufacturers can demonstrate that the alternate fuels (in flex-fuel vehicles) are actually being used.
Model year Allowable CAFE mpg increase
1993-2014 1.2
2015 1.0
2016 0.8
2017 0.6
2018 0.4
2019 0.2
After 2019 0.0
Read more:
http://www.motortrend.com/features/consumer/112_0907_cafe_explained/viewall.html#ixzz1vAqACHa2
