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" The EPA&amp;#039;s Role in Fuel Economy One confounding issue is that the CAFE (Corporate Average Fuel Economy) standards that the EPA has been tasked with enforcing are based on driving cycles codified in 1978. These CAFE mileages are not the same as the EPA city, highway and combined economy ratings you see on the window sticker when you&amp;#039;re shopping for a new car. The EPA has revised those mileages upward twice since 1978, in an attempt to make the numbers reflect a figure reasonably close to what one might actually see in the real world. As they say, your mileage may vary.  Comparing apples to apples, the 2016 CAFE numbers represent about a 20 percent increase in economy for cars and 24 percent for trucks. The new standards for cars will require a fleet average of 39 mpg, 30 for trucks. And the math to calculate that is pretty tough sledding: it&amp;#039;s not just simply a matter of multiplying EPA ratings by vehicle sales and striking an arithmetic average. Fleet fuel economy is calculated using the harmonic mean, not a simple arithmetic mean. The harmonic mean is the reciprocal of the average of the reciprocals of the fuel economies of all of the vehicles in the fleet. For example, a fleet of 4 vehicles getting 15, 13, 17, and 100 mpg has a CAFE of slightly less than 19 mpg, while the arithmetic mean fuel economy of the fleet is 36.25 mpg. The harmonic mean captures the fuel economy of the fleet for driving each car in the fleet for 1 mile while the arithmetic mean captures the fuel economy of the fleet for driving each car until 1 gallon of gas is burned (i.e., the 13-mpg vehicle would be driven for 13 miles while the 100-mpg vehicle would be driven for 100 miles). Why do we care how bureaucrats do their sums? Bottom line to this calculation is that extremely high-mileage vehicles (like a Volt or some other PHEV) have a smaller impact on fleet economy. One or two vehicles that get poor economy, like a full-size SUV or a high-performance car, can consume enough fuel to require the automakers to sell a lot full of 40-plus mpg cars to compensate. Hiking the fleet average, consequently, might require changing the mix of vehicles in the fleet, as well as hiking the economy of the vehicles comprising the fleet. Loopholes in the CAFE Standards On the other hand, here are plenty of loopholes in the law. CAFE standards have traditionally been full of end runs. (One example: flex-fuel vehicles. Sell enough E85-capable cars--even if they&amp;#039;re never ever fueled with E85--and your CAFE requirements are relaxed by as much as 1.2 mpg, fleet-wide). There is provision for larger trucks to have slightly poorer economy than smaller trucks, but the fleet must still average 30 mpg. Manufacturers can bank and borrow CAFE credits for three years if they can&amp;#039;t make the numbers in any single year. There&amp;#039;s a lot of fine print, and automakers have always worked the system, actually underachieving the mandated standards some years in the past. A few cars--diesels and hybrids--can achieve this improved economy now. Big SUVS and even full-size minivans will need an injection of improved technology to get better economy, or smaller, more fuel-efficient engines, which translates to poorer freeway merging and passing acceleration. That directly affects safety. Any improved technology that can deliver a 24 percent--or better--improvement in economy will have to be developed within the next 24 months, to allow the industry three years to bring new vehicles into production in time to make the deadline. One candidate is the Chevy Cruze, available now in Europe, powered by normally aspirated 1.6- and 1.8-liter powerplants, as well as a 2.0-liter turbodiesel. Planned introduction of the Cruze in the U.S. as a 2011 model will be in about a year. In Europe, the diesel engine Cruze costs about $2000 more than the gas engine cars. The engine slated for the U.S. version--which should easily deliver fuel economy to meet the new standards and then some--is a 1.4-liter turbocharged direct injection unit. Prices haven&amp;#039;t been set, but GM&amp;#039;s costs for the high-tech engine might be similar to the costs of the turbodiesel, which also boasts direct injection and a turbocharger. Ford&amp;#039;s Ecoboost technology is similar--turbochargers mated to smaller engines to achieve improved economy without reducing power or torque. The 2010 Flex is rated a 16 mpg city and 22 mpg highway with its normally aspirated V6 and AWD. Adding the two turbochargers and direct injection boosts the city mpg to 18, and the power from 268 to 355. It also boosts the price. Although 2010 Flex prices haven&amp;#039;t been released, 2010 Lincoln MKS (which shares its drivetrain with the Flex) prices have. Parsing through the optional equipment that becomes standard when you order the blowers puts the incremental price of the Ecoboost system at between two and three grand. In addition to more efficient powertrains, we&amp;#039;ll need, on average, smaller (for improved aerodynamics) and lighter cars and trucks. That means using more high-tech materials like carbon fiber and aluminum and magnesium. High-strength steel is already in increasing use. The Steel Marketing Development Institute just released a study predicting a 10 percent growth in the use of advanced high-strength steel, eventually culminating in the replacement of 650 pounds of mild steel with 350 pounds of ultra-high-strength steel to meet the 35mpg CAFE standards.  The Life-of-Vehicle Cost Reduction Supposedly, owners will save $2800 over the life of the vehicle, due to reduced fuel costs. Let&amp;#039;s do that math ourselves. The proposed increase, fleetwide, is 20 percent for cars. Drive your 30-mpg 2008 Honda Civic for 12,000 miles in a year, about the national average. It&amp;#039;ll consume, roughly, 400 gallons of gasoline. A 2016 Civic Hybrid will get around 40 or better, using 300 gallons, or maybe a little less, depending on how much Honda tweaks the drivetrain in the next five years. Savings: a convenient-to-remember 100 gallons, which would save around $250 annually with this week&amp;#039;s fuel prices. In 150,000 miles, you&amp;#039;ll save $3100. If the incremental price of the hybrid system to boost the fuel economy is $600, as the EPA has predicted, you&amp;#039;ll be ahead of the game about $2500, close to that predicted $2800. If and when gas prices increase, even better. The problem with this calculation: The price break for hybrids industry-wide is closer to $4000, not $600. None of the car companies we talked to would discuss their costs to install a hybrid drivetrain. But, if you compare cars with conventional drivetrains and their hybrid equivalents, the price increment on the sticker averages $4000. What about the tradesmen and landscape services and delivery trucks and families who have no other option than to drive large vehicles? Their options will necessarily dwindle and increase in cost. One dually pickup with a big V8--an absolute necessity when you&amp;#039;re hauling an RV or other heavy load along the Interstate--will offset the mileage numbers of more than a dozen 50-mpg Smart diesel hybrids. How is CAFE enforced? The current penalty for failing to meet CAFE standards is $5.50 per tenth of an mpg under the target value times the total volume of those vehicles in the affected fleet, (i.e., import or domestic passenger car, or light truck), manufactured for a given model year. Since 1983, manufacturers have paid more than $675 million in CAFE civil penalties. The consumer ultimately winds up paying that bill in the form of increased car and truck prices. Want to see what the U.S. fleet will look like in a generation? Go to Europe, which already achieves an aggregate fuel economy close to what&amp;#039;s in store for us here. It&amp;#039;s mostly small, fuel-efficient cars with small engines. More than 50 percent of the vehicles in Europe are diesels, too. Of course, Europe has always enjoyed the ultra-low-sulfur diesel we&amp;#039;ve only had available here since 2006. Europe has achieved its high-economy fleet without CAFE standards, simply because fuel has traditionally been far more expensive there than in the U.S.  RELATED STORIES * PLUS: The Road to 35 MPG From SAE  * ANALYSIS: Why the 35 MPG Is a Bad Idea  * EARLIER: Auto X-Prize Top 10 Teams  * OP-ED: The Ethanol Fallacy  * FOLLOW US: Popular Mechanics is Now on Twitter!  * FRIEND US: Find PM on Facebook   (Photograph by C.J. Burton) "^^<http://www.w3.org/2001/XMLSchema#string>
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