The fastest convertible ever on the 'Ring? Get the full story inside.

A new rumor is spreading that the Porsche 918 Spyder finished a lap at the Nurburgring in 7m 20s.  If true, the laptime would be a record for non-series production droptops, and all the more impressive by the car's low emissions of 70g of CO2 per km.

The rumor comes from a forum post at Teamspeed, where an image was uploaded reportedly from a presentation by Ferdinand Piech.  Piech is the grandson of Porsche founder Ferdinand Porsche, and personally owns 13 percent of the brand.  He is also chairman of the Supervisory Board at VW.

No confirmation yet on the story, but it would be an incredible feat for Porsche.  In recent years, the automaker has come under fire by environmental groups for vehicles that have a high level of pollution.  Porsche has steadily improved vehicle emissions, but nothing to the degree of the hybrid 918.

The Porsche 918 Spyder uses a 493-horsepower (368-kW, 500-PS) V8 engine and three 40-kW electric motors that raise combined output to 708 hp (528 kW, 718 PS).  Although the car uses just 3.0 liters of fuel per 100 kilometers (78 mpg US, 94 mpg imperial), it races to 100 km/h in 3.2 seconds.

European pricing on the Porsche 918 Spyder is expected to be around a half-million euros.

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