so i was filling up with 89 octane 10% ethanol today (my usual fuel choice) for $3.45/g when i remembered thinking that at some point, paying and extra$0.10/g for straight gasoline is a better value. (in iowa 10% ethanol has been $.10/gal cheaper than straight gas for years)
but at what price are the fuels of equal value? i've heard E10 has 3-6% less btu's. even going with 3%, i'd be losing money paying more than $3/gal, i'm thinking. i've also heard that btu's don't necessarily indicate mpg, and that some ethanol can actually improve mileage. does mileage improve 3-6% using straight gasoline over 10% ethanol?
anyone else have helpful info on this, am i just a fool for running 10% ethanol?
EPA rating for the Nissan Titan with E10 is 13 MPG city.
EPA for the E85 version is 9 MPG!
Alcohol contains about 65-70% of the energy content of gasoline. This can be offset somewhat by the fact that you can increase the compression in the engine that runs on alcohol (like the Indy cars).
The new EPA ratings avoid attributing any of the mileage loss to the use of alcohol in fuel.
I have read that certain alcohol percentage concentrations could actually improve economy (hard to believe but certainly possible) and alcohol should raise the effective octane rating which would allow more advanced ignition timing.
Here in eastern Virginia I don't see any stations that offer straight gasoline.
I also noticed from personal experience that I used to be able to beat EPA ratings easily (old higher ratings) when using straight gasoline. It was much more difficult after the change to E10.
Now we are seeing the effects of the increased demand for agricultural products due to the E10 fuel, which could easily offset any gains as far as reduced oil imports. It sure seems like this would have been obvious to any sane person when you consider the billions of gallons of alcohol it requires to supply 10% of US fuel consumption.
Slightly off topic but much information is available about hybrids if you look at the EPA Hydraulic Hybrid developments. Some good information about aerodynamic drag losses, graphs that demonstrate the peak efficiency potential of engines (gas and diesel). They have a mule hydraulic hybrid that weighs 3800 pounds that gets 80 MPG,
Here in Western Wisconsin, most gas pumps have the tag saying "May contain up to 10% ethanol", so you can't really be sure if it has ethanol, or exactly how much. But I make it a point to fill up at pumps that indicate no ethanol in the blend, as my past experience is poorer fuel mileage and idling problems when using the ethanol blends.
I believe that most fuels in Wisconsin probably contain some ethanol as an oxygenate. I don't know at what point they are forced to carry the label. There are areas, as over here in Waukesha county, where we are mandated to have RFG fuels that increase costs and maintain an amount of ethanol.
On another note, there was all the big talk about how bad MTBE was, and now MTBE was a problem. But MTBE is one of the main oxygenates used in racing fuels that are oxygenated. Not ethanol, but MTBE. One can actually get power from MTBE, but since it's a petroleum product and doesn't get double dipped by reducing mileage often to increase the tax revenue and then subsidized, it's been attacked.
I am originally from Nebraska, and, yeah, it was a choice there just like Iowa. You could buy the cheaper 89 octane fuel with ethanol, it's cheaper because tax payers pay to subsidize it, or the more expensive 87 octane.
I don't like mandates that reduce my ability to choose.
but at what price are the fuels of equal value? i've heard E10 has 3-6% less btu's. even going with 3%, i'd be losing money paying more than $3/gal, i'm thinking.
This is clearly a YMMV thing, as some cars react better to E10 than others. Because while E10 does have slightly less BTUs, it does have other desirable burn properties (higher octane for example) that can in some cars overshadow the BTU loss (and in some cases actually increase FE in some cars). For example, my car doesn't seem to care much if it has E10 or not, and sometimes even gets better FE with E10 than it does with plain gas. Which kind of makes it hard to generalize, as each car behaves differently to E10.
However, if you assume that just the BTU difference is the only factor (and as already mentioned its not), the break even math works out to:
So, again assuming the assumptions of a 4% loss for E10 are correct, you get "break even" if/when your gas_price is equal to (E10_price divided by 0.96). Likewise, gas would be a better deal (again assuming those assumptions) if/when "gas_price < (E10_price / 0.96)", and E10 should be the better deal if/when "gas_price > (E10_price / 0.96)".
Again, that's just the math involved. Feel free to plug in your own numbers (with your own assumptions), and figure out what price differential makes it most "cost effective" for you. Likewise, remember that it's not all about BTUs, and so your assumptions (and therefore the math, above) might not reflect reality in any given car.