A large vehicle with air bags and a leveling system that controls air flow into and out of an air spring (also known as an “air bag”) to maintain the air spring height close to the optimum level. The system is altered at minimum cost to further minimize the repeated flow of air into and out of the air spring, to thereby save fuel. A mechanical-to-electrical converter (50) is mounted on the air spring height sensor to generate an electrical signal indicating vehicle ride height, and the electrical output is connected to a computer (62) on the vehicle. The computer is programmed to control the flow of pressured air through a blocking valve (60) to a leveling valve (22) that flows air into and out of the air spring, according to the outputs of a plurality of sensors on the vehicle.