weight reduction

[niky]

Not sure. But my guesstimate, given your common 1100 kilogram compact sedan is about 100-150 kilograms... which, on your common car, would mean the removal of a whole lotta stuff. Removing carpets and sound insulation (those hard-packed asphalt strips stuck to the body under the carpet) should save you about 20 kilos. Replacing the spare with a donut or space saver spare saves about 8-10 kilos and removing it altogether about 16-20 kilos.

To reach about 150 kgs weight savings, you remove all the seats but the driver's seat, remove the AC hardware, and change some of the body panels to fiberglass. At worst, you'll need to replace some of the glass with plexiglass and remove the power window hardware.

This will primarily affect city fuel economy. Highway fuel economy will be relatively unaffected, as today's modern, extremely heavy cars, actually get decent fuel mileage on the NLEX. Reducing drag matters more here... in which case, you will want to create a front undertray that will not flex too much at high speeds, a rear undertray to keep air pressure from building up inside the rear bumper, and those fins that keep air from going into the wheel wells, as well.

Smaller side mirrors, with a sleeker design, help, as do consitently tight panel gaps... taping up the seams between panels helps reduce drag, too...