1990 Kenworth T600A
The T600 was a radical shift in truck design compared to its cousin the W900 (from which it was based). The major difference between the two was the massive aerodynamic face lift the T600 received, which resulted in up to 22% better fuel economy due to decreased drag.
Design for the T600 began in the mid 1970s (during the 1973 oil crisis) with Paccar researchers experimenting with wax models in wind tunnels. The T600 was replaced by the Kenworth T660 in 2008, which featured smoother styling.