Two Roadranger Spicer tag axles allow conversion of a 6×2 arrangement into a 6×4 configuration or a 6×4 into a 6×2 arrangement, with fuel economy improvements made up to 3 percent, the company says. Mechanical drivetrain loss has been decreased in the new axles, and the total weight is about 400 lb. lighter than the traditional 40,000-lb. tandem arrangement. The single-axle design requires 14 fewer pints of lubrication over 6×4 tandem axles.