GM cars are certified to run on up to 10% ethanol
... anything over that is not supported or recommended - unless the vehicle is designated as Flex Fuel capable
... I find it interesting that the EPA can require extensive and costly testing by manufactures to guaranty their vehicles will meet emissions standards, for a minimum number of miles, and then arbitrarily change the fuel to one that they were never certified to run on, or to meet those emission standards with.
General Motors’ position regarding the Environmental Protection Agency announcement allowing the use of E 15 in 2007 and newer vehicles:
The vehicle Owner Manual specifies that fuels containing more than 10 percent ethanol should not be used in GM vehicles that do not have a flex fuel designation.
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[TD]GM has the largest fleet of flex fuel vehicles on the road today (over 4 million in the U.S.) and these vehicles can safely use ethanol blends of up to 85 percent ethanol. So blends of E 15 (15 percent ethanol), as in the partial waiver announced, are appropriate for these vehicles. However, ethanol blends greater than E 10 should not be used in GM vehicles that do not have a flex fuel designation as they are not designed and certified to run on gasoline consisting of more than 10 percent ethanol-blend volume to avoid any unintended consequences, as per: their Owner Manual.
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