1960 and after: For the next 20 years, the Detroit Diesel and Allison Divisions grew, tripling sales during the 1960s alone. 1962: Production and marketing of remaining Cleveland Diesel products moved to GM's Electro-Motive Division, leaving Detroit Diesel Engine Division the remaining partner of GMDD. 1965: GMDD structures absorbed into the Detroit Diesel Engine Division, formally ending GMDD as a separate entity. Detroit Diesel introduces the Series 149 engine for use in workboats, push boats, and 100 ton-plus mining trucks. 1970: General Motors consolidated Detroit Diesel with the closely allied transmission and gas turbine businesses of the Allison Division, forming the Detroit Diesel-Allison Division. 1974: The Series 92 engine was introduced, called the Fuel Squeezers; the 6V-92TT engine achieved fuel savings of 10% to 20% over previous models of comparable horsepower. During the energy crisis, turbine engines became uncompetitive. 1980: Detroit Diesel-Allison produced its first four-cycle engine. A few years later in the early 1980s diesel engine production split off as Detroit Diesel Division while turbine engines remained as Allison Division. 1987: The Series 60 — the four-cycle heavy-duty engine for which the company is well known — was introduced. It was the first production engine to have integrated electronic controls as a standard feature. The Series 60 was cleaner and more fuel-efficient than previous heavy-duty engines, and became the biggest selling heavy-duty diesel engine in the North American Class 8 truck market. 1988 January 1: A joint venture between Penske Corporation and General Motors created Detroit Diesel Corporation. Penske had a 60% majority ownership in the new venture and the CEO was former racecar driver Roger Penske. 1993 October: Detroit Diesel Corporation had grown its on-highway heavy-duty market share to 33% from 3% only a few years earlier. The company also made an initial public offering of common stock, becoming a publicly traded company listed on the New York Stock Exchange under the stock symbol "DDC". That same year, Detroit Diesel launched the Series 50, the first Detroit Diesel natural gas engine. 1999: Detroit Diesel built its 4 millionth engine. 2000: In October 2000, DaimlerChrysler bought Detroit Diesel Corporation. 2000: Off-highway engines combined with MTU Friedrichshafen to form MTU America The on-highway division of Detroit Diesel was retained by DaimlerChrysler (now Daimler AG) as part of Daimler Trucks North America (DTNA). 2005: Detroit Diesel Corporation invested $350 million to refurbish and retool its plant for future business. 2006: MTU