A small fleet of test rigs waited outside, and each tractor packed a 14-liter 455-horsepower Series 60 and pulled a 53-foot Utility van ballasted to take each close to the 80,000-pound legal maximum.

Fast-forward to February, 2006. Detroit Diesel and Freightliner have already completed more than 5.2 million test miles on the Series 60 engine – well ahead of schedule to complete 14.8 million miles ...

As a result, Detroit Allison built their first four-stroke engine in 1989, known as the Series 60. In the years following its release, the Series 60 became the best-selling four-stroke commercial ...