standards, Navistar began to phase out MaxxForce diesel engines in favor of Cummins-produced engines. In the CE, the Cummins ISB6.7 was introduced as an option for 2014 production, becoming the standard engine for 2015. For the RE, the MaxxForce DT was replaced by a Cummins L9 diesel, with a Cummins B6.7 introduced during 2018 for the CE. In the mid-2010s, IC centralized production around school buses. After 2014, the AE/AC, BE, and LC were discontinued. For 2018, the HC was replaced by the TC (as the MV replaced the DuraStar); within the shuttle bus segment, IC reverted to a role of chassis provider, no longer producing completely-bodied vehicles. Alongside the TC medium-duty cutaway cab, IC Bus currently produces the CE and RE-series as school buses/MFSABs (activity buses); both model lines are also offered in commercial applications (derived from the school bus bodies). Alternative-fuel strategy In the United States, Navistar was the sole diesel engine manufacturer to pursue the use of exhaust gas recirculation (EGR) to control diesel emissions rather than selective catalytic reduction (SCR). The company claimed EGR posed an advantage in overall fluid economy (measuring combined diesel + urea consumption), although separate testing resulted in an advantage with SCR. In 2015, IC debuted its first alternative-fuel vehicle, showing a propane-powered CE-Series with a PSI 8.8L V8 engine. In 2016, the same engine was introduced in a gasoline-fueled configuration. Electric bus On November 7, 2017, IC Bus announced the chargE, an all-electric CE Series bus delivering up to in power using a Volkswagen Truck & Bus Group-supplied common group electric drivetrain. It is the second electric vehicle to be delivered from the Navistar-Volkswagen alliance. The chargE started production in 2019 2020s For 2022, IC Bus would undergo another overhaul of its product line. It was announced that the RE Series will be discontinued in 2024, leaving IC Bus solely as a Type C only manufacturer. Products School/commercial buses Model designations Prior to 2010, IC used the following nomenclature (on school buses) to designate the engine type; subsequently, only the model prefix has been used. Prototype vehicles Forward Advantage Prototype The IC FE Forward Advantage was a school bus prototype built by IC in 2008 as a testbed of a "flat-floor" design in the stepwell due to the compact design of the Caterpillar C7 engine. It also included some front-end styling modifications influenced by the severe-service line of International trucks. As