Nov. 9--The paper sign taped to the Fuel Zone gas pump reads: 100 percent unleaded gasoline. No ethanol added.

It's an attempt to lure customers who believe ethanol blends hurt engine performance, and it's effective with drivers like Daniel Campbell. The Athens resident prefers pure gasoline to the 10 percent ethanol blend in his 1968 Camaro, which has a high-performance engine.

"I'm a car enthusiast, and I hear it is harmful," he said of the ethanol blend. "But I'm curious, what's the truth?"

Ethanol proponents make scientific arguments that the corn-based product is more efficient. Some local mechanics, including an automotive repair teacher, however, assert ethanol blends lower fuel economy.

The 10 percent ethanol blend, or E-10 gas, is more prevalent in local stations, including name brand fuels, Chevron and Texaco.

Nine of the 14 stations on Sixth Avenue Southeast in Decatur sell ethanol-added fuels now. Statewide, there is about an 80 percent increase in E-10 availability this year. That number is expected to grow as refiners increase ethanol use as part of a federal mandate.

While all U.S. vehicles dating to 1970 can burn E-10 gas, there are differences. E-10 produces less carbon monoxide, so it's considered better for the environment. But it contains less stored energy, measured in BTUs, than pure gasoline, which leads to the debate about whether E-10 has less gas mileage than pure gasoline.

Strictly from a BTUs standpoint, E-10 blends should have a 3 percent loss of energy compared to pure gasoline.

J.B. Smith, president and chief financial officer for The Ethanol Corp. in Birmingham, said the difference in E-10 and pure gasoline is negligible.

While ethanol has fewer BTUs than gasoline, it counters that by increasing the efficiency of the gas it's blended with, he said. This occurs because ethanol adds oxygen to the fuel, improving combustion.

"Ethanol makes sure you use all the hydrocarbons in gasoline," Smith said. "So you don't have unburned hydrocarbons blowing out the tailpipe."

Sherman Leeth, automotive technologies teacher at Austin High School, however, is convinced E-10 gas does measurably lower gas mileage.

Statistics project

A graduate-level statistics project he conducted at Alabama A&M University in 2005 showed his 6-cylinder Jeep Cherokee got 3 percent less fuel mileage, he said.

He drove the same vehicle 350 miles from home to work and home again, so it was the same driving conditions. His vehicle featured a mileage computer that automatically tracked fuel consumption.