FTC on MPG-decline vs. ethanol content

[gone-ot]

Some (short, 3 page) reading on FTC.GOV about decline in fuel economy vs. ethanol content:

http://www.ftc.gov/sites/default/fil...7105-00022.pdf

[Ecky]

Knoll, et. al.3 tested 16 conventional vehicles using splash blends of ethanol in certification gasoline and showed a linear fuel economy decline with ethanol.

This is counter to what some forum members have been saying.

EDIT:

...(E10) will have about 3.3% less energy than the base gasoline, a 20% blend of ethanol in gasoline (E20) will have about 6.6% less energy than the base gasoline...

...E10 resulted in a 3.7% decline in fuel economy and E20 resulted in a 7.7% decline.

[roosterk0031]

Plenty of other studies with way better data that disagree, don't feel like finding them again. U of Nebraska, U of a Dakota. I have 30,000+ miles that disagree as well.

[Cobb]

Ive been mixing some e85 into my tank. I find some makes the mpg go down, more makes it go up. 6 gallon e85 vs 4 gallons e10 for a tank is a good mix.

[thomason2wheels]

That seems counterintuitive given the lower btu content of ethanol but I realize there are other variables inplay here... but even so...any idea why that works better than straight e10?

[gone-ot]

...because the refineries *use* the higher octane rating of ethanol when they "blend" lower-grade gasoline to make E10 = 87 octane.

[thomason2wheels]

So in pther words the octane kick from the ethanol combined with lower grade gasoline gives more overall btu content?

[Baltothewolf]

If E20 was 20% cheaper and gave 7.7% less MPG, I could live with that.

[gone-ot]

Originally Posted by thomason2wheels

So in pther words the octane kick from the ethanol combined with lower grade gasoline gives more overall btu content?

In a round-about way, yes, but the "...more overall BTU content..." comes more from the density of the lower octane gasoline feedstock, which they *blend* UP with enough ethanol (typically less than 10% as E10 label states) to achieve 87 octane rating...plus (or minus) the butane they add/subtract for winter/summer RVP control per EPA regulations.

[ksa8907]

Originally Posted by thomason2wheels

That seems counterintuitive given the lower btu content of ethanol but I realize there are other variables inplay here... but even so...any idea why that works better than straight e10?

There are scientific reasons but essentially it simplifies to a faster and thus hotter burn. The amount of ethanol reauired to see a gain is dependant on engine design and ecu programming just to name a couple.