The International DuraStar (originally introduced as the International 4000 series), is a product line of medium-duty trucks produced by Navistar International from 2001 to 2018. Introduced as the successor to the International 4000 series of 1989–2001, the 4000 series was renamed the DuraStar in 2008. Developed as a Class 6-7 product range, the 4000/DuraStar was slotted below the 8000/TranStar regional-haul semitractor, with the Class 5 International TerraStar (2010–2015) serving as the smallest International conventional-cab product range. The most distinctive features of the DuraStar are the "crescent shape" headlights and a distinctive "black spot" on the left side of the cab. Produced as both a semitractor and a straight/rigid truck, the 4000/DuraStar has been used in a wide variety of applications, including emergency vehicles, towing, flatbed trucks, and cargo box trucks. For bus use, the chassis is used in both cowled-chassis and cutaway-cab configurations for school bus and commercial applications. For 2019 production, the International DuraStar underwent an extensive revision, becoming the International MV. Blue Diamond Truck alliance From 2001 to 2009, Navistar medium-duty trucks were assembled as part of a joint venture with Ford Motor Company. Named Blue Diamond Truck, LLC, the 50/50 joint venture between Ford and International developed medium-duty trucks for both companies assembled in a Navistar facility in General Escobedo, Mexico. Upon a shared chassis, Ford and Navistar produced distinct cabs and interiors. While Ford supplied its medium-duty Ford F-Series with Cummins and Caterpillar engines, the International 4000/DuraStar was (initially) supplied with International-designed diesel engines (DT, VT, MaxxForce). In 2000, Ford introduced the medium-duty Ford F-Series (the F-650/F-750 Super Duty), with International introducing its 4000 series truck line in early 2001. First generation (2001–2018) In February 2001, Navistar released its all-new 4000 series, dubbed as "High Performance Trucks". Developed in the Blue Diamond Truck joint venture with Ford, the 4000 series marked the first completely new truck line from International since the 1979 S series. Sharing its chassis with the medium-duty Ford F-Series (introduced in 2000), the International 4300/4400 retained the DT466 and DT530 diesels of their predecessors. For versions equipped with automatic transmissions, electronics for the engine and transmissions were retuned to optimize throttle and shifting response, to increase both performance and fuel economy. To increase forward visibility, the size of the windshield was increased by over 60%, with additional attention paid to improvements in ventilation. At the launch of the 4000 series, the standard 4300