Unleaded vs E85 break even point--cost/efficiency

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#1
What is the break even point comparing the cost of unleaded vs the cost of E85? Unleaded fuel burns more efficiently than E85. But E85 is always cheaper. Around the Chicago area E85 is about 60 to 80 cents cheaper per gallon. At what price difference does it make economical sense to buy E85? Assuming one has a flex fuel vehicle. Price difference of $0.90? $1.00?
 
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#3
Thanks for your reply, but most everyone knows that. There is a pricing point where E85 is more economical to buy than regular unleaded. Is that a price difference of a $1.00/gal, $2.00/gal.? Where is the break even point?
 

billr

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#4
It is not going to be a simple one-size-fits-all $ number. Based on the heat content of the two fuels it should be a %, so that would have to be applied to current prices for the two fuels; a moving target. Worse, though, is that it will also depend on the specific engine design, condition of the engine, and driving conditions; that magic number could vary from day-to-day. Your best info will be empirical data from driving through several tanks of each different type.
 
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#6
It is not going to be a simple one-size-fits-all $ number. Based on the heat content of the two fuels it should be a %, so that would have to be applied to current prices for the two fuels; a moving target. Worse, though, is that it will also depend on the specific engine design, condition of the engine, and driving conditions; that magic number could vary from day-to-day. Your best info will be empirical data from driving through several tanks of each different type.
I tend to agree with the percentage measurements. Generally speaking, how much more efficient is regular unleaded vs E85? Once that percentage is known, it's an easy calculation,

For the sake of argument, let's say regular unleaded is 25% more efficient than E85. Then E85 would have to have more than a 25% difference in price than E85 to save money on fuel.

Now I ask, what is the percentage difference?
 

billr

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#8
My understanding is that E85 in the USA may have 51-83% ethanol. That is a wide range, you are going to need to analyze fuel from the E85 pump at time of purchase to even make use of knowing energy in it relative to cost.