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Hey all (back again). I was thumbing through some articles and trying to calculate the fuel/oil savings of having a FFV (since Krogers now has E85 in Houston). I'd already gotten a Prius this month, so my decision was already made, but wanted to see how much worse the Prius was compared to a small 2007 E85 sedan in terms of oil consumption.

Assumptions (partially referenced).
I think some of the "Regular Unleaded" here in Houston is E10.
To produce 10 gal of Ethonal requires 1 gal of gas (tractor gas?).
I'll use the Prius to gather figures for E10.
I'll use the Chrysler Sebring to gather figures for E85.
I'm assuming EPA mileage (they test E85 mileage too).

==
Prius E10 FE estimate = 55 mpg

Take a 100 mi test run.
Prius will consume 1.82 gal E10
of which 1.64 gal will be E0 and 0.18 gal will be E100.
To provide the 0.18 gal of E100, it will cost an additional .02 gal gas in processing costs.
So the total gas (E0) consumed will be 1.64 + 0.02 = 1.66 gal.

This translates to 60 miles per gallon of E0 consumed.

==
Sebring E85 FE estimate = 18 mpg

Take a 100 mi test run.
Sebring will consume 5.56 gal E85
of which 0.83 gal will be E0 and 4.72 gal will be E100.
To provide the 4.72 gal of E100, it will cost an additional 0.47 gal gas in processing costs.
So the total gas (E0) consumed will be 0.83 + 0.47 = 1.30 gal.

This translates to 76.6 miles per gallon of E0 consumed.

Another factor to consider is pollution. Overall the amount of pollution generated by bringing 1 gal of E85 to market and consuming it, is very comparable to the same cycle for regular gas. So the Sebring burning 3 times as much fuel produces 3 times as many emissions (at least). It will also cost much more to operate compared to a hybrid.

So all in all, the Hybrid -vs- FFV debate can be summarized as this:

Hybrids consume about 25% more oil than a FFV.
Hybrids produce 65% less pollution than FFV.
Hybrids cost 40% less to operate than FFV.

For me, these were the three factors to consider (consumption, pollution, cost). Based on consumption alone, definitely go FFV. Pollution and cost are big motivators for me as well. Hopefully by the time I'm in the market for a new car (2017) they will have a Plug-in Flex Fuel Hybrid Prius for me.

<edit>
These calcs assumed a 9:1 production cost of ethanol (ie to bring 9 gals of ethanol to market, you consume 1 gal of gas... tractor gas?). Turns out this ratio is hotly debated. Some say it's as low as 7:1 or 5:1. Well just for the record, at a ratio of 11:2 or 5.5:1 the Prius and the Sebring consume the same amount of oil based gas.
</edit>

References:
http://rael.berkeley.edu/ebamm/FarrellEthanolScience012706.pdf
http://en.wikipedia.org/wiki/Flexible-fuel_vehicle
http://www.fueleconomy.gov/feg/2001cartablef.jsp?id=23842
http://www.fueleconomy.gov/feg/2001cartablef.jsp?id=23599
http://www.latimes.com/business/la-fi-hybrid8jan08,0,2452416.story?coll=la-home-headlines

By 2017 I will guarantee that there will be a FFV hybrid. Heck, Ford has been taunting us with an E85 Ford Escape hybrid.

Dan,

You are ahead with a hybrid over a flex-fuel vehicle. I have concerns on how E85 will be implemented. I'd like to see more flex-fuel cars - not just trucks. Would also like to see the the focus on celluistic ethanhol, so it does not impact the food and water supply.

I know it's a double post... but here goes. I added an edit to my original calcs after someone contested my original ethanol production cost of 9:1.

Here's the edit:
These calcs assumed a 9:1 production cost of ethanol (ie to bring 9 gals of ethanol to market, you consume 1 gal of gas... tractor gas?). Turns out this ratio is hotly debated. Some say it's as low as 7:1 or 5:1. Well just for the record, at a ratio of 11:2 or 5.5:1 the Prius and the Sebring consume the same amount of oil based gas.