Iowa Code § 279.34: Motor vehicles required to operate on ethanol blended gasoline.

A motor vehicle purchased by or used under the direction of the board of directors to provide services to a school corporation shall not operate on gasoline other than ethanol blended gasoline as defined in section 214A.1. The motor vehicle shall also be affixed with a brightly visible sticker which notifies the traveling public that the motor vehicle is being operated on ethanol blended gasoline. However, the sticker is not required to be affixed to an unmarked vehicle used for purposes of providing law enforcement or security.