Octane: What's in Your Fuel?

by Kris Bevill (Ethanol Producer Magazine) Minimum octane rating decisions could greatly impact ethanol’s future market opportunities
At a time when ethanol’s high-octane rating is touted as its most valuable asset, a situation in South Dakota shows a lower-octane gasoline scenario could also emerge. In March, officials at South Dakota’s Office of Weights and Measures began receiving calls from members of the state’s petroleum industry, warning that cheaper 85 octane gasoline had been making its way from the higher elevations in the western part of the state, where it has been historically sold, and into areas where the minimum octane rating is 87. South Dakota, like other states, requires octane labeling, and there was concern that the subgrade 85 octane was being marketed as 87 octane to unsuspecting customers.
...The use of 85 octane gasoline dates back to carbureted vehicles manufactured before 1984. Engine knock was known to occur in that type of engine due to a number of factors, with altitude being one of the most significant. The American Society for Testing and Materials identified regions, primarily in the Rocky Mountains, where lower octane gasoline performed as well in those engines as 87 octane at sea level, and to this day, 85 octane is sold in those regions, despite the fact that vehicles now use computer-controlled systems unaffected by high altitudes.
...No vehicles are currently approved for use with fuel containing an octane level below 87, and because the 85 octane fuel being used in South Dakota is being blended with ethanol, there is concern that ethanol will take the blame for vehicle damage actually caused by lower octane gasoline.
...Increasing fuel economy standards for vehicles will require auto manufacturers to design smaller, more efficient engines that continue to satisfy the consumer’s desire for power. Some automakers have already begun introducing these types of engines into the market, the most well-known being General Motors Co.’s Ecotec engine and Ford Motor Co.’s Ecoboost engine. High-octane fuels have been shown to be the most effective fuel for these types of engines, and some experts have suggested that higher octane gasoline could be beneficial in existing engines as well. Ford researchers noted in a March article in the scientific journal Fuel, that while more research is needed to quantify and optimize the costs and benefits, “substantial societal benefits” may be realized by capitalizing on ethanol’s high-octane rating.
... The researchers state that higher minimum octane ratings would enable higher compression ratios in future vehicles, improving efficiency, and benefit all spark-ignited engines and hybrid vehicles. “Incorporating ethanol with its inherent high-octane rating is one opportunity to enable an increase in the minimum octane rating for regular-grade fuel,” they said.
Anderson and his colleagues point out that despite increasing blending of ethanol into the nation’s gasoline, the octane ratings of regular gasoline have remained unchanged for 40 years. The researchers attribute this lack of octane increase to petroleum companies modifying their base fuels to take full advantage of ethanol’s octane at a 10 percent blend. In the paper, Anderson’s group says that even if ethanol content is increased, the oil industry can be expected to continue to reduce the octane ratings of its blend stocks so that the final product meets minimum octane requirements, unless government policies raise the minimum octane rating. And, because automakers design the vast majority of their vehicles to operate on the minimum octane rating, the opportunity to increase vehicle efficiencies through the use of higher octane gasoline is limited. “If vehicle manufacturers knew with certainty that the minimum octane rating of fuel would increase at a known future date and remain at these levels, it would be possible to provide future engines that are designed with higher [compression ratios] and operate with correspondingly higher thermal efficiencies, which could also provide the potential for engine downsizing and turbocharging to further improve fuel economy,” the researchers said. READ MORE and MORE (Ethanol Producer Magazine) Download Fuel study Download SAE study

Excerpt from Ethanol Producer Magazine's The Wyoming Oil Embargo of 2012: ...So just add 10 percent ethanol to the 85 octane gas, and it will have an octane rating above 87, right? Nope. A few months ago, some of the refineries quit making a straight 85-octane regular unleaded gasoline, and their primary product now is an 82-ish octane base fuel which they then blend with 10 percent ethanol to get an 85 octane E10. Adding 10 percent more ethanol to that E10 would make it E20, which can’t be used legally in standard cars (and we know how oil companies feel about replacing gas—even low-octane stuff—with more ethanol).
Refiners claim they made the change to offset the cost of the renewable fuels standard, conveniently leaving out the fact that because ethanol costs less than gas, E10 made with the 85-octane straight gas they were previously making would actually save them six to ten cents. The truth is that making 82-octane is more profitable, and doing so gives the refiner control of ethanol blending. READ MORE