Porsche's claims take advantage of NEDC rules that allow them to start with a full battery on the city loop. EPA would classify electric efficiency and gas efficiency separately.
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Obviously, the Mustang is not a sports car. It's a two-door sedan.
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But more seriously, sportscar shmortscar. The exclusive term ain't nothing but a body-style, considering there are four-door sedans that can whip traditional sports cars in terms of both power and handling, and most traditional "sportscars" are actually 2+2 coupes now. The traditional definition is 1- or 2- seat only, open-topped and low-slung. Which means, from the list given, the Corvette and Z4 are the only ones that count.