I think someone at VW has been reading the ecomodder forums. There is aparaently a new gasoline powered Bluemotion Passat which gets 40mpg. Which is a lot for a gas engine in a car that big. Quoted from treehugger.com
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VW BlueMotion Passat Technical Specifications
The 1.4 liter TSI engine features both a turbo and direct injection, and is rated at 122-horsepower. CO2 emissions are 136-138 g/km, and the car can be had with a 7-speed direct-shift gearbox (DSG) transmission. It also has low-rolling resistance tires, longer gear ratio than the non-BlueMotion model, "a chassis thats been dropped 15 mm, a fully enclosed underbody, a closed grille and a weight reduction of 30 kg"."
Article here