Yahoo Autos What is Flex Fuel? The pros and cons of flexible fuel vehicles
On the surface, Flex Fuel sounds like a great idea. Certain cars that are designed for it can run on a variety of blends of gasoline and ethanol. OK, we all know gasoline, but what is ethanol then? It is a type of alcohol derived from crops like corn or sugarcane. Ethanol fuel came about as a response to oil shortages, starting in the 1970s, and eventually became an important market for grain farmers. Flex Fuel engine technology didn't really mature until the 1990s, and automakers, mostly the Big Three, began introducing flexible fuel vehicles.
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What is Flex Fuel?
Specially equipped vehicles designated as Flex Fuel capable can operate on E85, a mix that can contain from 51% to 83% ethanol and just the remainder as gasoline. However, to a lesser degree, nearly all modern cars are already using a gasoline-ethanol mix. Most gasoline sold at pumps in the U.S. could technically be E10, a 10% ethanol blend, though it isn't always.
The EPA has also approved E15, a 15% ethanol blend. However, in 2012 a coalition of automakers pushed back against the proposal to increase ethanol content by 50%. The EPA deems E15 safe to use in 2001 and newer cars, but there has been conflicting research on whether or not it is damaging. Many automakers said at the time that they would not honor warranties if owners used E15.
Flex Fuel pros
By stretching the amount of actual gasoline used, Flex Fuel seems like the perfect solution for extending a finite resource and reducing dependence on foreign oil. And since the ethanol was derived from renewable biomass, it was originally seen as a green solution as well.
In addition, E85 has an octane rating of about 110, higher than the 93 octane of premium fuel. That means the fuel can better resist earlier-than-expected combustion caused by compression and thus burns more completely, and a cleaner burn means fewer emissions at the tailpipe. While performance engines typically have higher compression ratios, the current crop of E85-compatible vehicles are not exactly sporting machines that can take advantage of the higher octane.
Because Flex Fuels use less petroleum, they are cheaper. At the time of this writing, the national average for E85 is about 80 cents less than E10, the most common type of fuel. Prices will vary by region, so check your local listings.
Flex Fuel cons
It may seem like a no-brainer to use E85 if you have a Flex Fuel vehicle in times of high gas prices. However, it should be noted that ethanol reduces fuel economy (miles per gallon) by as much as 25% to 30%. Depending on the vehicle's mpg rating and the local price of E85, drivers will have to determine for themselves whether the reduced fuel economy negates any potential savings at the pump.
