DETROIT -- In a world of higher octane gasoline -- in which 95 would replace 87 and become the new regular -- automakers could more easily and affordably meet stringent fuel economy standards as well as reduce carbon dioxide emissions.
During a panel discussion this week at the SAE World Congress here, representatives from Ford Motor Co., General Motors, Chevron Energy Technology Co. and an ethanol trade group agreed that raising octane would allow gasoline engines to run more efficiently, boosting fuel economy between 3 and 6 percent and lowering CO2 emissions by around 2 percent.
Octane is a measurement of a fuel's resistance to igniting when compressed in an engine's cylinder. Raising octane allows engineers to increase the engine's compression ratio, which in turn enables an engine to run with greater thermal efficiency and produce more power from less fuel.
Increasing compression in an engine is a quick, easy and inexpensive change that can usually be accomplished with slightly reshaped pistons or modifications to the cylinder head.
But high octane gasoline costs significantly more than regular -- about 37 cents per gallon on average this week, according to the U.S. Energy Information Administration. That gulf has grown in recent years as premium gasoline's share of the market has decreased to roughly 13 percent. Automakers are reluctant to force consumers to pay more for gasoline and have not been lobbying for higher octane. But that could be changing.
With the government-mandated fleet average fuel economy standards gradually increasing to 54.5 mpg in the 2025 model year, automakers are running out of inexpensive ways to boost fuel economy.
Panel moderator Dean Tomazic, FEV Inc.'s vice president of passenger car and light-duty engines, said raising the compression ratio from 8:1 to 12:1 could yield as much as a 10 percent gain in fuel economy in some engines burning 102 octane "super premium," a grade available in Germany.
Stephen Gill, Ford's chief engineer for engine systems, said his engineers tested a high compression 3.5-liter twin turbo V-6, such as the one used in the F-150 pickup, and recorded efficiency gains of nearly 5 percent.
Panelist Amir Maria, a research engineer for Chevron Energy Technology Co., said there would be little benefit for most drivers if 87 octane were replaced with 95 because most of the today's vehicles have been calibrated to run on 87 octane.
"Raising octane would have little impact on the current fleet," he said. "At 25 cents per gallon difference, the cost to the consumer to use premium adds $1,500 over 200,000 miles."