DEF diesel engines

Cat tried to save money by claiming that their ACERT technology cleaned up the exhaust so they didn't need after engine cleanup. In order to pass EPA mandated testing they cut back on power and fuel consumption. This worked on the dyno but not in the truck. By the time DEF was used by Cummins and Detroit in 2010, emissions were mandated in off road machinery. Cat was fined millions of dollars for falsifying their truck engine tests so they stopped production of on-road engines. Cat then sold their truck engine manufacturing to Navistar who produced Cat C-13, C=15 engines under their own name for several years until the EPA forced them to stop. Cat still makes off road equipment engines that meet EPA regulations but I don't know how they do it. Incidentally, DEF is so good at cleaning up diesel exhaust it allowed engine manufacturers to raise the horsepower by adding fuel and letting the DEF clean it up.