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Old 06-25-2013, 08:56 AM   #46
Studly Adventurer
Joined: Feb 2011
Location: Collinsville, OK
Oddometer: 950
There is a real loss in gas mileage and power when using ethanol laced fuel. In addition to having less energy content than gasoline, ethanol also carries a significantly different stoichiometric ratio. Gasoline, as we all know, burns cleanest, makes the least emissions, and generally gives the best gas mileage at 14.7:1. Ethanol on the other hand, has a stoichiometric ratio of 9:1. ALmost all modern cars religiously target the 14.7:1 ratio that gas loves and they may dip down as low as about 13:1 under heavy load. It's fairly obvious that the ethanol mixed gas causes the air fuel mix to run outside of it's intended operating stoich ratio. This in combination with ethanol's lower energy content gives a reduction in power and fuel economy that doesn't really work in an expected linear fashion.

As preciously mentioned by one of the other posters, many of the auto tuning shops have taken to a liking E85. This is predominantly because of they typically work on forced induction cars that require higher octanes than normal gas in order to increase the boost safely. Race gas is very expensive so their defacto choice is to use E85 which has a similar octane rating but costs much less. To use E85 and make more power requires big injectors, big fuel pumps, and big boost to take advantage of that pesky 9:1 stoich ratio. Unfortunately this also gives abysmal gas mileage, often times getting 2/3 or less mpg for similar power levels with straight gas.
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