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Is Ethanol Robbing Me Of MPG?

As you may know, the Commonwealth of Virginia mandates 10% ethanol in every station's fuel tanks. :rolleyes:

I've been told this costs us about 10% on efficiency. :mad:

What do the experts here say? :confused:

Yes. Ethanol provides less energy per unit volume, and the A/F ratios are not the same, so more ethanol is consumed.

This has been known since carburetor days when larger jets had to be used when running ethanol.

Bollocks!

Is it harder on an engine that isn't a "FlexFuel" vehicle? I'm pretty sure the German engineers who designed my car in the 1980's didn't do so with 10% ethanol in mind.

It'll make it run a bit leaner, but probably not 10% leaner, as the ECU has adjustment available. I don't think 10% counts as "flex fuel" anyhow.

10% seems like a bit much. I loose about 2 mpg or so on the Matrix when using E10. They do this because ethanol burns cleaner than gasoline.

Comparing the energy content of ethanol and gas, E10 has 3.2% less energy per gallon. It raises the octane, though, so, as always, YMMV. Studies have shown reductions in the 2-3% range.

Quote:

Originally Posted by PaleMelanesian (Post 38616)

Comparing the energy content of ethanol and gas, E10 has 3.2% less energy per gallon. It raises the octane, though, so, as always, YMMV. Studies have shown reductions in the 2-3% range.

Higher octane than necessary reduces efficiency, as the burn is cooler. Increased octane is of no benefit if there is no pinging/detonation or the ignition can't be advanced to take advantage of it.

Quote:

Originally Posted by Shawn D. (Post 38617)

Higher octane than necessary reduces efficiency, as the burn is cooler. Increased octane is of no benefit if there is no pinging/detonation or the ignition can't be advanced to take advantage of it.

While this is true, I think it's fair to say 87 octane e10 is 87 octane in the same was the 87 octane non-ethanol gas was 87 octane before the ethanol mandates.

Hello,

I believe that ethanol adds some necessary oxygen to the mix, so it burns cleaner. Whatever the reason, it is there -- something has to replace the MBTE since that crap was/is messing up the groundwater.

Interesting to note, MTBE has about 80% the energy of gas, while ethanol has about 67%. So moving from an MTBE mix to ethanol is about the same drop as moving from straight gas to MTBE.

http://www.epa.gov/otaq/regs/fuels/ostp-3.pdf

Quote:

As can be seen in Table 3-1, the theoretically expected decrease in fuel energy as a result of oxygenate use is in the 2% to 3% range when compared to gasoline. This corresponds to 0.5 to 0.8 miles per gallon for a car that averages 27 miles per gallon. As can be seen from the works cited below, research in this area indicates that any fuel economy loss experienced as a result of oxygenate use agrees with the theoretical prediction for fuel energy loss. Thus, it is reasonable to conclude that any fuel economy loss experienced with oxygenate use is solely a function of the change in fuel composition and the resulting slight decrease in energy content of the fuel.

http://tonto.eia.doe.gov/oog/info/twip/twip.asp

Quote:

MTBE and ethanol contain about 80 percent and 67 percent, respectively, of the energy in conventional petroleum-based gasoline. The result is that typical oxygenate blending reduces the Btu content of gasoline by two to three percent.