Do you really want to run your car on ethanol? Isn’t it a whole lot better for the environment? There are a few things you should know before pulling up to the pump.

The use of ethanol as an automobile fuel isn’t anything new. In 1925, Henry Ford told a New York Times reporter that “ethyl alcohol is the fuel of the future.”

Today, ethanol is commonly used as an additive to gasoline. Although pure ethanol could be used to run a combustion engine, we’re not there yet. Using pure ethanol, also known as E100, requires an engine specifically designed for this purpose – your car isn’t likely one of them. You can, however, use ethanol blended with gasoline and many cars on the road today do just that.

Ethanol is mixed with gasoline in varying quantities to produce a blended fuel product, which you probably know of as gasohol. Two common mixtures in the U.S. are E10 and E85, 10% and 85% ethanol, respectively.

In general, the higher the ethanol component of a gasohol blend, the lower its suitability for most gasoline-powered cars on the road today. Pure ethanol degrades rubber and plastic engine materials and must not be used unless the vehicle was specifically designed for it’s use.

Additionally, pure ethanol has a much higher octane rating than ordinary gasoline, which requires changes to the compression ratio or spark timing. To change a gasoline-fueled car into a pure-ethanol-fueled car, larger carburetor jets are also necessary.

Engines running on pure ethanol also need a cold-starting system to ensure the vehicle runs correctly when the temperature drops below 55 °F. On the other hand, if only 10 to 30% ethanol is mixed with gasoline, engine modifications are typically unnecessary.

Several auto manufacturers are building “flexible-fuel” vehicles equipped with fuel sensors that automatically adjust to the fuel in the system. In 1993 through 1995, Chrysler offered flexible-fuel versions of the Dodge Spirit and Plymouth Acclaim. Some Chrysler minivans were also offered at that time.

In 1998, GM introduced their first light truck (an S10) in a flexible-fuel configuration. Ford introduced a flexible-fuel option on it’s Ford Ranger pickup trucks in 1999. Other manufacturers such as Mercedes-Benz also offer flexible-fuel vehicles and the 2007 C230 Sport sedan is one of the newest vehicles promoted in this category.

What about fuel mileage?

Word of caution, ethanol contains less energy per gallon than gasoline. The end result is a reduction in fuel economy (MPG) by 34% if you ran on pure ethanol instead of gasoline, but you’re not so let’s look at reality.

For a blended fuel such as E10 (10% ethanol and 90% gasoline), the effect is small – about 3% lower MPG than good old gasoline. However, for E85 (85% ethanol), the reduction is significant. With E85 in the tank, you’ll travel about 27% fewer miles per gallon. Lower MPG requires more frequent refueling stops and a little accounting.

What’s a better buy, a gallon of gas at $3.00 or a gallon of ethanol at $2.20?

You need to take into consideration the lower MPG figures for ethanol to answer this question. If regular gasoline costs $3.00 per gallon, and E85 costs $2.20 per gallon, the two are essentially the same cost per mile driven. If the discount for E85 is less than 27%, it actually costs more per mile to use it.

Research is being conducted to increase fuel efficiency by optimizing engines for ethanol-based fuels. One approach is to use ethanol’s higher octane to increase the engine’s compression ratio. Currently, there are no commercially available vehicles that make significant use of advanced technologies for this purpose, but this will likely change in the near future.

Environmental considerations are another factor. In many cases, ethanol is considered a renewable resource, but is it better for the environment? There is an on-going debate concerning the answer to this question – one I’ll answer in another post.

[tags] ethanol, flexible fuel, auto, blended fuels, E85, E10, E100, alternative fuels,, eoecho [/tags]