A Tesla logo sits on the wheel hub of a Tesla Inc. Model S electric vehicle at a Supercharger station in Egerkingen, Switzerland. (Photographer: Stefan Wermuth/Bloomberg)

GM and Fiat Chrysler Unmasked as Tesla's Secret Source of Cash

(Bloomberg) -- For years, Tesla Inc. has hauled in revenue by selling credits to other carmakers that needed to offset sales of polluting vehicles to U.S. consumers. These sorts of transactions hav...