According to the Department of Energy, a gallon of E85 has about 72 percent to 77 percent of the equivalent energy compared to what’s in a gallon a gasoline. So, if you have a flex-fuel vehicle and opt for E85, you will actually get worse fuel economy than when you use premium gasoline. For example, a 2009 Chevrolet Impala that’s rated with a combined 23 mpg when using gasoline drops to 17 mpg in combined fuel economy when using E85.
The difference between “Regular” and “Premium” unleaded gas has to do with the octane ratings. The octane rating for gasoline ranges from 84-93, with premium usually having a 93 rating. E85 has an octane rating of 100-plus, which is great for performance cars but the fuel itself simply isn’t as energy dense as gas. You have to use more of it to travel the same distance as you would with gasoline.
According to the DOE, E85 is typically cheaper than gas and its emissions are generally less than that of gasoline. See below for a complete list of E85 capable cars for 2009 as well as a calculator tool to help you figure out the cost advantage of E85 vs. gasoline and the pounds of greenhouse gases saved.
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