DETROIT — President Obama announced new automobile fuel-efficiency standards on Friday that require an average 54.5 miles per gallon by 2025. But even if the auto industry manages to meet the new standards, it is unlikely car buyers will see many fuel-economy stickers with such high mileage.

Instead, the average new vehicle in 2025 will probably be closer to 43 miles per gallon, based on the typical 20-percent discount applied by federal officials when rating a car or truck in real-world driving conditions.

That’s one example of how new corporate average fuel economy rules, known as CAFE, will require considerable interpretation for the industry and consumers alike.

Administration officials said Friday that the new fuel rules also contained an intricate set of “credits” for auto companies to achieve the new target of 54.5 miles per gallon for their fleets in 14 years.