Discuss as:

Supercars with style

The super-efficient cars of the future don't all have to look like glorified motorcycles. Illuminati Motor Works' swoopy Seven, for example, looks as if it were beamed down from a retro "Dick Tracy" universe, complete with gull-wing doors and an aerodynamic teardrop profile. The Seven was among, um, seven cars that went through fuel-efficiency road tests today at the Michigan International Speedway in Brooklyn, Mich., as part of the Knockout stage of the $10 million Progressive Insurance Automotive X Prize competition. (We previewed the Knockout drag-down on Sunday.)

Other teams that were put through their paces included TW4XP, Enginer, Western Washington University, Global-E, Li-ion Motors and FVT Racing. The X Prize Foundation's Cristin Lindsay posted pictures from the scene throughout the day. Two cars are listed on the X Prize website as being eliminated so far during this stage: Liberty Motors Group's Liberator and K-Way MOTUS. Stefano Carabelli, team leader for Italy's K-Way automakers, took a philosophical stance in a video clip explaining that engine problems doomed their attempt to win the prize: "We tried. We failed. So far."

Twenty-six cars are still in the running. So far. Check out the X Prize Twitter feed for updates from Tuesday's round of efficiency test drives, and click through our X Prize auto slideshow to see some of the other competitors.

X Prize cars

X Prize Foundation

Illuminati Motor Works, Team TW4XP and Enginer line up their X Prize cars for efficiency test runs on Monday.