Thread: E15
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Old 04-01-2019, 08:56 PM   #4
fdryer
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Join Date: Jan 2006
Location: NYC
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2003 L-Series 3.0L Sedan
Default Re: E15

If anyone were to examine pricing a gallon of 100% antifreeze against the same gallon but as a 50/50 blend of premixed water and antifreeze, there's a definite disparity. Two gallons of 50/50 premix costs more than one gallon of 100% antifreeze. The one gallon cut with another gallon of water makes two gallons of premix, costing less than buying two gallons of premixed coolant. A similar cost analysis applies to using regular 100% gasoline compared to 10% or 15% ethanol added to gasoline but becomes clouded over by cost comparison unless fuel mileage is applied.

For all intents and purposes, using 100% gasoline (zero ethanol) is the basis for all other costs and fuel mileage comparisons. Costs per gallon and fuel mileage must be taken together to appreciate any real or false benefits. Making things easier might be comparing 10% ethanol/fuel mileage to 15% ethanol/fuel mileage.

A full tank of 10% ethanol costs and total mileage used is compared to a full tank of 15% ethanol used and total mileage. Costs and fuel mileage are now compared to arrive at values reflecting any positive or negative benefits.

In reality, adding ethanol lowers fuel mileage by a few miles compared to 100% gasoline. Adding another 5% ethanol lowers fuel mileage some more. Per gallon costs isn't useful for comparison. Full tank costs and total fuel mileage are compared between 10% and 15% for a better perspective.

In combustion discussions, more ethanol is needed than gasoline per combustion cycle. Air fuel ratios for gasoline is always 14.7:1 - 14.7 parts air to one part fuel. Ethanol air/fuel ratios are around 9:1 - nine parts air to one part ethanol. More ethanol is needed to burn in one cycle compared to gasoline. In heat numbers, gasoline has about 115,000 BTUs while ethanol has about 76,100 BTUs. Ethanol has less heat energy compared to gasoline and needs to be fed in greater amounts per engine combustion cycle. This translates to using more ethanol than gasoline from an air fuel ratio. Going from 10% to 15% ethanol in gasoline is simply lowering fuel mileage no matter what the costs as no one in the petrochemical business is giving anyone discounts on fuel no matter what's said or advertised.

I used the premix antifreeze cost comparison to 100% antifreeze as an example of false advertising to bring honest fuel costs/fuel mileage for a greater perspective when considering 10% to 15% ethanol/gasoline comparisons. Diluting 100% gasoline lowers fuel mileage, period.
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