A few weeks ago reports emerged that the 2010 Porsche Panamera would be just efficient enough to squeak by without incurring the gas guzzler tax penalty, a happy thought for potential owners. Today at a Panamera drive event, Porsche confirmed to High Gear Media that the car will indeed sidestep the tax.

It just barely clears the required mark, however, with a combined fuel economy rating of 23 mpg across the range for purposes of the tax. That's only 0.5 mpg above the floor for avoiding the tax.

How the 2010 Panamera managed to secure a 23 mpg combined average isn't clear, as the sportier S and 4S models score 16 mpg in the city and 24 mpg on the highway, hinting at a combined score closer to 20 mpg. The Turbo knocks another 1 mpg off each of those figures.

If combined efficiency of a passenger car dips anywhere below 22.5 mpg, the tax starts at $1,000 and quickly ramps up from there, hitting $3,000 below 17.5 mpg and maxing out at $7,700 for cars averaging less than 12.5 mpg.

The gas guzzler tax was formulated in the late 1970s and revised in 1991, but SUVs, pickups and commercial vehicles are still excluded from its scope, meaning only passenger cars are subject to the tax.