Honda increased the vehicle's fuel efficiency using aluminum and plastic extensively to reduce the vehicle's weight. The basic structure is a new, lightweight aluminum monocoque, reinforced in key areas with aluminum extrusions joined at cast aluminum lugs. Stamped aluminum panels are welded onto this structure to form an extremely light and rigid platform for the drivetrain and suspension. The Insight has a body weight less than half that of the contemporary Civic 3-door, with increased torsional rigidity by 38% and bending rigidity by 13%. Honda built the Insight with aluminum front brake calipers and rear brake drums, and with a largely aluminum suspension, in addition to standard aluminum wheels; reducing the ratio of un-sprung to sprung weight as well as the total weight. The fuel tank is plastic; the engine mounts are aluminum; and the exhaust is a small, thin wall pipe. Its compact spare is also aluminum. The Insight weighed in manual transmission form without air conditioning, with manual transmission and air conditioning, or with CVT and air conditioning.