May 2009 Issue
Avoiding Ethanol: Easy Tests Do the Trick
If youíre burning mogas, STCs donít permit any ethanol content. But more service stations are selling only E10, so hereís how to check your supply.
As the number of aircraft engines capable of using automobile gasolineómogasórises, so does pilot interest in using it instead of pricier 100LL. And the next time oil prices spike, as they did during the summer of 2008, interest will be greater. But the increasing alcohol content in mogas, coupled with less-stringent quality control when compared to 100LL, makes it impossible to know exactly what youíre getting. That alcohol, specifically ethanol, may not be a problem if youíre driving a car or truck manufactured in the last couple of decades. But for those aircraft engines approved for mogas, thereís a catch: Few of them allow large percentages of ethanol. And if youíre flying an older aircraft using mogas under a supplemental type certificate, none of them allow it. To be sure what youíre putting in your tanks, you need to test the fuel for its ethanol content. Blending ethanol into mogas has its roots in the gas crises of the 1970s, but really didnít get going until the late 199 0s. New U.S. air-quality rules enacted early in that decade reduced allowable carbon monoxide levels and refiners started adding methyl tertiary butyl ether (MTBE) as an oxygenate to meet the requirements. Soon, however, MTBE was blamed for contaminating groundwater and, as of 2006, it had been banned in 20 states, although no federal ban currently exists. States and localities still had to comply with air quality rules, so ethanol became the oxygenate of choice. Presently, renewable fuel standards in nine states require blending ethanol with mogas, according to the American Coalition for Ethanol. Fourteen states have incentives for marketing ethanol-blended fuels and many more have on the books various incentives supporting ethanol production. Despite questions about its economics and energy required to produce it in the U.S., ethanolís presence in mogas likely will increase.
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