Ahead of the official announcements of the improved performance of the 2017 Paccar MX-11 and MX-13 engines, along with a new proprietary tandem axle that is designed to be the industry’s lightest and most efficient axle in its class, Peterbilt Motors. Co. invited Fleet Owner to its Denton, Texas, assembly plant for a preview and test drive of the powertrain combo in a fully equipped 2017 Model 579 EPIQ marketing vehicle.