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In the last couple of years, petrol companies have started offering petrol with 10% ethanol in them, presumably at a cheaper price than normal unleaded.

However, I've noticed (although this is just from a gut feeling), that my car when using fuel with 10% ethanol in it, seems to use up the fuel much faster.

does ethanol actually save you money? Is it better for the environment?

Has anyone done any tests to see if the fuel economy is the same with ethanol fuel vs normal unleaded?

Cause if it is 10% less efficient, isn't that a false economy? You might as well just buy 10% less normal petrol - in fact, it'll be better cause your car will weigh less because you're carrying around less fuel.

  • It would be nice to specify your country. In my country we produce ethanol in large-scale, and the ethanol cost-benefit is better, but this may vary, from country to country. – hooray May 21 '11 at 19:23
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    @Lennart : Regardless of whether it's a fossil fuel, aren't you still burning it hence creating CO2 when you drive? – Samuelson May 21 '11 at 23:12
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    @Samuelson: Yes, you create CO2 when you burn it. However, this is CO2 the plants just pulled out of the atmosphere, thus, you aren't adding to the CO2 overall (except for fossil fuels the machines burned that were used for cultivating the plants). – Jonas May 22 '11 at 1:04
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    I seriously doubt that ethanol would be cheaper if you disregard government subsidies, though. And it has the drawback of effectively using up food to make fuel. But now we are getting off-topic. :-) – Lennart Regebro May 22 '11 at 6:57
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    Given that fuel price is about 90% taxes, question "is it cheaper" cannot be really answered, as it depends on local taxation rules. – vartec Jul 19 '11 at 9:21
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This is a complicated question, because there are many variables to consider.

  1. Which ethanol are you talking about? There are many ways to make ethanol, some more efficient than others, and with different environmental impacts. Many studies seem to indicate that corn-based ethanol, which currently is most popular in the U.S., is not a very efficient way to produce ethanol. But there are many other feedstocks--sugar cane, potatoes, and other grains are also common in some places. Even sawdust.

    Read about some estimates of the true cost of corn-based ethanol.

  2. If you are only asking about the cost of fuel per mile, then consider that ethanol contains about 33% less energy by volume, compared to gasoline. This means that to break even, financially, in terms of cost-per-mile, you must pay 33% less for ethanol versus gasoline. For E10 (10% ethanol, 90% gasoline), that means you would need to pay 3.3% less (than for 100% gasoline)

  3. Different fuels require different hardware. To run E85, for instance, you need a flex-fuel vehicle, which may have different manufacturing costs than a "standard" gasoline-only vehicle.

  4. Ethanol also has a different octane rating than gasoline, which can affect engine performance (positively or negatively, depending on your engine specifications). Over long periods of time, this may either positively or negatively impact the cost associated with maintenance on your engine.

  5. Different fuels may have difference maintenance-related costs associated with them, such as the types of fuel filters, pumps, injectors, timings, etc, that must be used (some of this is covered by the "flex-fuel" system, of course, which I already mentioned). And different fuel types may lead to failures--and thus replacement costs--of some of these systems more rapidly than others.

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