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Chevy's 6.6-liter Duramax is pretty much all new

To say there's a heated battle in heavy-duty pickups is an understatement, with Chevrolet, Ford, and Ram constantly trading blows of increased torque, horsepower, and towing capacity. The latest salvo is the revised, more powerful turbo diesel 6.6-liter Duramax V8 in the 2017 Chevy Silverado. It has 910 pound-feet of torque, an increase of 145, putting it nearly level with the Ford Super Duty. Here's a closer look at where those gains come from. How exactly did Chevrolet add all that torque plus 48 horsepower? The automaker essentially took a fine-tooth comb to the entire engine. Chevy says it changed 90 percent of the V8, and the cumulative effect of those small changes adds up to big increases. As you might guess, the turbocharger is updated. The larger unit features electric actuation of the variable nozzle turbine (VNT), and what Chevy calls a double axle cartridge mechanism that separates the VNT moving parts from the housing. That helps with heat performance as well, with a claim that the exhaust side of the turbo can run continuously up to 1,436 degrees Fahrenheit. Helping that cause are six exhaust gaskets made of Inconel - an nickel alloy that contains chromium and iron – and upgraded stainless steel for the exhaust manifold. Despite having the same cast iron cylinder block, albeit with some minor enhancements, the engine has new cylinder heads, pistons, piston pins, connecting rods, and crankshaft, which have all been upgraded to handle 20 percent higher cylinder pressures. Alongside the increase in pressure, Chevrolet also increased the cylinder head's structure with a honeycomb design. The pattern features high-strength aluminum with dual layer water jackets that not only improve strength, but also optimize water flow for better cooling. For 2017, the cylinder head also benefits from integrated plenum that aids the engine in getting more air under heavy loads. The cylinder head isn't the only component to get a minor update, as the pistons have a larger diameter pin for improved oil flow. The same detailed improvements has been bestowed to the humble connecting rods (second in our hearts only to the inanimate carbon rod). The new design has the bolts oriented roughly 45-degrees to the rod instead of parallel. The angle split design, as it's called allows for easier passage through the cylinder.

GM seeks national mandate for zero-emissions cars

DETROIT — General Motors says it will ask the federal government for one national gas mileage standard, including a requirement that a percentage of auto companies' sales be zero-emissions vehicles. Mark Reuss, GM's executive vice president of product development, said the company will propose that a certain percentage of nationwide sales be made up of vehicles that run on electricity or hydrogen fuel cells. GM says a nationwide program modeled on such a requirement in California could result in 7 million electric vehicles, or EVs, on U.S. roads by 2030. California wants 15.4 percent of vehicle sales by 2025 to be EVs or other zero emission vehicles. Nine other states, including Maryland, Massachusetts, New Jersey and New York, have adopted those requirements. In January, California Governor Jerry Brown set a target of 5 million zero-emission vehicles in California by 2030. The Trump administration criticizes California's ZEV mandate, saying it requires automakers to spend tens of billions of dollars developing vehicles that most consumers do not want, only to sell them at a loss. Reuss told reporters that governments and industries in Asia and Europe "are working together to enact policies now to hasten the shift to an all-electric future. It's very simple: America has the opportunity to lead in the technologies of the future." A national mandate also would create jobs and reduce fuel consumption, CO2 emissions and "make EVs more affordable," Reuss added. GM, the nation's largest automaker, will spell out the request Friday in written comments on a Trump administration proposal to roll back Obama-era fuel economy and emissions standards, freezing them at 2020 levels instead of gradually making them tougher. Under a regulation finalized by the Environmental Protection Agency at the end of the Obama administration, the fleet of new automobiles would have to get 36 miles per gallon by 2025, 10 mpg higher than the current requirement. But the Trump administration's preferred plan is to freeze the standards starting in 2021. Administration officials say waiving the tougher fuel efficiency requirements would make vehicles more affordable, which would get safer cars into consumer hands more quickly. GM on Thursday said it doesn't support the freeze, but wants flexibility to deal with consumers' shift from cars to less-efficient SUVs and trucks.

These are the 'Greenest' and 'Meanest' cars in 2015

As has become tradition, the American Council for an Energy-Efficient Economy (ACEEE) has come up with a ranking of what it refers to as the "greenest" cars of 2015, and, by way of contrast, a list of the so-called "meanest" cars, so those who value eco-friendliness over all else can choose which vehicles they should or should not consider buying. As you may expect, electric cars make up the majority of the greenest cars on the list, but, perhaps surprisingly to many, the Tesla Model S didn't make the cut. It's worth noting, too, that where the electricity an owner uses to charge their electric vehicle has a big impact on its overall environmental impact. "A car that is charged using electricity generated from natural gas or renewables is going to have significantly less impact on the environment than one charged on a coal-heavy grid," says ACEEE lead vehicle analyst Shruti Vaidyanathan. The ACEEE's list for 2015 looks very different than it did in 2014. It's an interesting collection, though – and we're sure this goes without saying, really – we'd recommend doing a bit more research into each vehicle and how it might fit into your daily life before making any purchase decisions. Click here to see the ACEEE's list of the Greenest and Meanest vehicles sold in the United States in 2015. Green Bugatti Chevrolet Fiat GM GMC Mercedes-Benz Nissan RAM smart Toyota greenest greenest cars