This means someone who wants a front-drive Flex can get one for as little as $29,270, but the least expensive Flex with EcoBoost is an AWD SEL, costing $36,890. Whether Flex buyers choose the Duratec or EcoBoost, AWD Flexes get 16 mpg city and 22 on the highway.The Duratec’s six-speed automatic remains unchanged, but the version backing the EcoBoost was strengthened to handle the increased torque.