In fact, the federal government mandated in the 1990s that MTBE be blended into gasoline to increase octane and improve combustion.

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Technologies such as internal combustion engines and gas turbines will continue to improve gradually in efficiency but they are familiar and developed.

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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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