Peterbilt Motors Company announced a new optimized drivetrain package for its already fuel-efficient leader, the aerodynamic Model 579, that brings even greater levels of fuel economy, the company announced during the Mid-America Trucking Show. Called APEX, the new spec option pairs the PACCAR MX-13 Engine with the Fuller Advantage Automated Transmission. The combination features optimized shift calibration, weight savings and proprietary control logic between the two components. “This is a winning combination for our customers looking to get even more miles per gallon from their already fuel efficient Model 579,” said Darrin Siver, Peterbilt General Manager and PACCAR Vice President. “It assists drivers with error-free shifting that means even a fleets’ novice drivers can operate with the fuel efficiency of more expert drivers.” APEX is available now available for order through the Peterbilt dealer network. According to Peterbilt Chief Engineer Landon Sproull, APEX can result in up to a 4 percent improvement in fuel efficiency versus previous drivetrains. Superior fuel economy is achieved, he said, through the precise fuel management resulting from proprietary communication technology. “APEX results in exceptional performance and fuel economy by pairing two already fuel efficient components together and optimizing the way they communicate to reach even greater levels of savings,” said Sproull. “This is a fully integrated powertrain that is packaged in our flagship Model 579, which is already exceeding customer expectations for fuel efficiency.” The 12.9 liter PACCAR MX-13 Engine and the 13-speed Fuller Advantage share critical data including torque, operating gear and other vehicle performance metrics. Additionally, Sproull said, APEX is more than 80 pounds lighter than previous combinations and features a small-step ratio in 9 th and 10 th gears for a more fuel efficient operating range while downshifting. The PACCAR MX-13 Engine is available with 380 to 500 horsepower and up to 1,850 ft-lb of torque.