Flex-fuel chartHow bad is ethanol for your engine? There's been a lot of debate on this issue as the US considers upping the biofuel content in the national gasoline supply from 10 percent (E10) to 15 percent (E15). The ethanol industry and some scientists say higher ethanol blends show no "meaningful differences" in new engines while the oil industry says ethanol creates health risks. Researchers working at the Ford Research and Innovation Center decided to take a closer look at how a wide range of gas-ethanol blends - E0, E10, E20, E30, E40, E55 and E80 - affected the emissions coming out of a flex-fuel 2006 Mercury Grand Marquis.

To see the full report, printed in the journal Environmental Science & Technology, requires payment, but there is an abstract and Green Car Congress has some more details. The gist is that, "with increasing ethanol content in the fuel, the tailpipe emissions of ethanol, acetaldehyde, formaldehyde, methane, and ammonia increased." At least NOx and NMHC emissions decreased. The researchers say that the effects are due to the fuel and "are expected for all FFVs," but that the way that a manufacturer calibrates the engine will affect NOx, THC, and NMOG emissions.

It's this last bit that's important, since the researchers found, "Higher ethanol content in gasoline affects several fundamental fuel properties that can impact emissions. ... These changes can have positive or negative effects that can depend on engine design, hardware, and control strategy. In addition to direct emissions impacts, higher ethanol content fuel can also provide more efficient combustion and overall engine operation under part-load conditions and under knock-limited higher-load conditions." So, as we head towards more ethanol in our fuel supply (maybe), manufacturers are going to need to learn how to burn it most efficiently.

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