Think the Caterham Seven roadster was only good for track days and carving up country lanes You're absolutely correct, but the company found out if you also slap on a bunch of aerodynamic gear and skinny tires, you can get one to hit 131 miles per gallon (though, to be fair, that's probably those bloated UK royal gallons). Still, it's a matter of bragging rights for the roadstermaker, which showed off its eco-minded prototype at the recent Shell Eco-Marathon at Rockingham. The concept was based on Caterham's outgoing 1.6-liter Rover K Series engine (the new models have Ford engines), with a carbon-fiber aero kit from Axon Automotive. A company rep also said they used "careful driving" to blast through the original target of 100 mpg.