Mr. ERON SHOSTECK (Alliance of Automobile Manufacturers): Carbon dioxide is a direct byproduct of a vehicle's fuel combustion.

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Cars like the Buick Encore, Fiat 500 and Lincoln MKZ, meanwhile, improve mileage through direct fuel injection, which injects gas directly into the combustion chamber in extremely precise amounts.

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Now, it's true that amazing gains are being made in the efficiency of internal combustion engines, both gas and diesel: direct injection, cylinder deactivation, stop-start, eco-mode throttle mapping, to name a few of the recent applied technologies.

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