Optimal Ethanol Blend Level

A study¹ commissioned by the American Coalition for Ethanol found non-flex-fuel cars using ethanol blends in excess of 10%, returned much better fuel economy numbers than were expected. E10 - with 10% ethanol blended into gasoline is the typical amount of ethanol the motorist with a non-flex-fuel car could encounter at the pump.

In the HWFET testing , ethanol blend levels of E20 in the flex-fuel Chevrolet Impala, E30 in the non-flex fuel? Ford Fusion and Toyota Camry, and E40 in the non-flex-fuel Chevrolet Impala resulted in better fuel consumption or greater fuel economy greater than predicted based on per-gallon fuel BTU content and in some cases, better than gasoline. An FTP-75 was run (in triplicate) on all the test vehicles at these ethanol blend levels.

The University of North Dakota Energy & Environmental Research Center (EERC) and the Minnesota Center for Automotive Research (MnCAR) conducted vehicle fuel economy and emission testing on four 2007 model vehicles. The vehicles tested included a Chevrolet Impala flex-fuel and three non-flex-fuel vehicles: a Ford Fusion, a Toyota Camry, and a Chevrolet Impala. This investigation utilized a range of undenatured ethanol Tier 2 gasoline blend levels from 0% to 85%. The primary objective of the investigation was to investigate the possible existence of a fuel economy-based optimal ethanol blend level, as determined by the Highway Fuel Economy Test (HWFET), at which measured miles per gallon is greater than predicted based strictly on per-gallon fuel Btu content. A secondary objective was to acquire HWFET? hot-start tailpipe emission data for all surveyed fuels. Following optimal blend-level determination, cold-start emissions, as determined by Federal Test Procedure 75 (FTP-75), were determined on the optimal blend-level and Tier 2 gasoline.

While only three non-flex-fuel vehicles were tested in this study, there is a strong indication that non-flex-fuel vehicles operated on optimal ethanol blend levels, which are higher than the standard E10 blend, can obtain better fuel mileage than on gasoline. The Ford Fusion and Toyota Camry obtained a HWFET mileage on E30 of 1% greater than on straight Tier 2 gasoline; the flex-fuel Chevrolet Impala showed a HWFET mileage of 15% on E20 better than Tier 2 gasoline, as shown in Figure ES-1. Exhaust emission values for nonmethane organic gases (NMOG?), nitrogen oxides (NOx?), and carbon monoxide (CO) obtained from both the FTP-75 and the HWFET driving cycles were at or below U.S. Environmental Protection Agency (EPA) Tier 2, light-duty vehicle, Bin 5 levels of 0.090, 0.07, and 4.2 grams/mile, respectively, for all vehicles tested, with one exception. The flex-fuel Chevrolet Impala exceeded the NMOG standard for the FTP-75 on E20 and Tier 2 gasoline.

Cold-start emissions, as determined by FTP-75, were determined on the optimal blend level and Tier 2 gasoline. HWFET testing on ethanol blend levels of E20 in the flex-fuel Chevrolet Impala, E30 in the non-flex-fuel Ford Fusion and Toyota Camry, and E40 in the non-flex-fuel Chevrolet Impala resulted in miles-per-gallon fuel economy greater than predicted based on per-gallon fuel Btu content. It is notable that the non-flex-fuel vehicles obtained greater fuel economy at higher blends of ethanol than they were designed for. In the case of the flex-fuel Chevrolet Impala, the highway fuel economy was greater than calculated for all tested blends, with an especially high peak at E20. While only three non-flex-fuel vehicles were tested in this study, there is a strong indication that non-flex-fuel vehicles operated on optimal ethanol blend levels, which are higher than the standard E10 blend, can obtain better fuel mileage than predicted by fuel energy content. Exhaust emission values for NMOG, CO, and NOx obtained from both the FTP-75 and the HWFET driving cycles were at or below EPA Tier 2, light-duty vehicle, Bin 5 levels of 0.090, 0.07, and 4.2 grams/mile, respectively, for all vehicles tested with one exception. The flex-fuel Chevrolet Impala exceeded the NMOG standard for the FTP-75 on E20 and Tier 2 gasoline at 0.120 grams/mile and 0.152 grams/mile, respectively.

References:

¹Optimal ethanol blend-level investigation final report November 2007 by: Richard E. Shockey and Ted R. Aulich, Energy & Environmental Research Center, University of North Dakota. Also, by Bruce Jones, Gary Mead Paul Steevens, Minnesota Center for Automotive Research, Minnesota State University, Mankato, MN

External links:

American Coalition for Ethanol