— Detroit Diesel Corporation recently celebrated the shipment of its 75,000th Series 60 engine to Penske Truck Leasing (PTL). PTL took delivery of its first Series 60 engine in 1990 with a total order of 47 units.Since 1992, the Series 60 engine has been the most popular heavy-duty truck engine in the Class 8 market based on R.L. Polk registrations. One of the reasons for the popularity of this engine is its significant fuel economy savings over other engines in the same class. The Series 60 engine is available in vehicles produced by business units of Freightliner LLC and other premium vehicle manufacturers, such as those in the firetruck, emergency, motorcoach, and motorhome markets.