The 2021 Peterbilt 579 UltraLoft is built for serious over-the-road professionals who demand performance, comfort, and profitability in every mile. Whether you’re an independent owner-operator or managing a growing fleet, this truck is spec’d to maximize uptime, fuel efficiency, and driver satisfaction. Under the hood, you’ve got the proven Cummins X15 — one of the most respected engines on the road. Known for its durability, torque, and fuel efficiency, the X15 delivers the pulling power you need for heavy loads while keeping operating costs under control.The aerodynamic design of the 579 reduces drag and boosts fuel economy. Lightweight components increase payload capacity, helping you generate more revenue per trip. Peterbilt’s reputation for quality and resale value makes this truck a smart long-term investment. If you’re looking for a truck that works as hard as you do — one that keeps you comfortable, profitable, and on schedule — the 2021 Peterbilt 579 UltraLoft with a Cummins X15 and 12-speed Endurant transmission is ready to go the distance.