CAFE Fuel Efficiency Standards: 54 MPG Is Possible
By Mark Fischetti
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A new car in 2025 will go twice as far on a gallon of gasoline than a 2012 model does now, if automakers comply with new federal standards released today. The U.S. Environmental Protection Agency and the National Highway Traffic Safety Administration announced aggressive new rules to raise the fuel efficiency of cars, SUVs and pickup trucks. The Corporate Average Fuel Economy, or CAFE, standards require an automaker's fleet of passenger vehicles to average 54.5 mpg by 2025. That number extends existing CAFE rules, which set the fleet average at 35.5 mpg for 2016, up from the current level of 27.5 mpg.
Although many car companies said earlier this year that they would support the then-proposed CAFE goals, grumbling has ensued. Automakers have resisted CAFE increases since the early 1980s, each time protesting that redesigns and technology improvements needed to reach the new targets would either be too difficult to engineer or too expensive to manufacture. An additional chorus has arisen this time around, along the lines of "Well, the companies can only achieve such a jump in efficiency if something like one-third of their fleet is made up of all-electric vehicles, to pull up the average, and the public will not buy that many electric cars."
Both arguments are smokescreens.
Electric vehicles can certainly raise fleet averages. But changes to good ol' gasoline-powered vehicles can achieve a great portion of the needed hike in fuel efficiency. The kicker is that many of the technology improvements have been sitting on auto industry shelves for years. And some of the improvements have already been rolled out in high-end gasoline vehicles and in standard hybrid cars.
In the past, independent engineering studies by experts at M.I.T., the University of Michigan, Argonne National Laboratory and the Natural Resources Defense Council have shown that gasoline-powered vehicles can get dramatically higher mileage by incorporating a number of incremental changes. Among them are continuously variable transmissions, which replace the inefficient gear-based transmissions cars have used for a century; starter-alternators that turn the engine off whenever the car is idling, saving gas whether the vehicle is stopped at a traffic light or rolling down a hill; direct fuel injectors that sip less gasoline than conventional fuel injectors; and regenerative braking, which converts friction at the wheels into electricity.
Changes to engines themselves, made possible by advanced, high-power electronics, can also raise fuel economy significantly. Continuous valve timing decreases the fuel that an engine needs. Cylinder deactivation halts two cylinders in a six-cylinder engine when that power is not needed -- which occurs often when cars are cruising along at somewhat constant speed -- thereby burning less fuel. Conversely, turbochargers can give a four-cylinder car the power of six cylinders during the relatively few moments when hard acceleration is needed, such as passing a truck on a hill, allowing larger cars to function well with smaller engines, thus getting better mileage. Vehicles can also cut weight to consume less fuel. Many of the technologies and the efficiency gains they offer, along with illustrations of how they work, are described in a detailed February 2010 Scientific American article titled Better Mileage Now.
Indeed, the mass-market mileage champ, the Toyota Prius, uses this incremental approach. Although a hefty series of batteries provides power in various circumstances, that only gets the car part way to reaching 45 or 50 mpg. The Prius has a continuously variable transmission. It uses regenerative braking. It has the stop-start feature that turns the engine off instead of idling. It also has a highly aerodynamic shape that cuts air resistance, and it travels on so-called low-rolling-resistance tires that reduce losses from road friction. Every one of these features can be incorporated into cars that run only on gasoline. Some vehicles already have some of the improvements: Honda, for example, has used continuously variable transmissions for years in many of its high-mileage cars.
Furthermore, although the new CAFE numbers sound high, they translate into less taxing goals on the road. The mileage ratings come from running cars on machinery in labs that do only a fair job of mimicking actual road conditions.
"CAFE mpg still comes from the original pair of tests that are now widely viewed as bad predictors of real-world mpg. The 34.1 mpg CAFE target for 2016 is actually equal to only 26 mpg on a window sticker. The talked-about 2025 CAFE standard -- usually described as 54.5 mpg -- amounts to a figure of 36 mpg combined [highway and city driving] on a window sticker," writes Dan Edmunds, director of vehicle testing at Edmunds.com, on the company's detailed CAFE explainer. (The Edmunds.com site is widely recognized as the go-to place for investigating new and used cars and automotive technology.) So if you walk into a showroom in 2025 and see car with a sticker that says it gets 36 mpg "combined," it meets the CAFE 54.5 mpg requirement. Suddenly the new rules don't sound so difficult to attain.
As for fuel-efficient technologies being too expensive to incorporate, the new rules (pdf) allow automakers to obtain significant tax credits for rolling them out. For consumers, EPA and the highway administration estimate that the technology needed to create cars that get 54.5 mpg -- which will satisfy stiffer requirements for emitting fewer greenhouse gases -- will raise the price of a car by about $2,000 in 2025. But they also estimate that car owners will earn that money back in two to three years through savings at the gas pump.