Mack Trucks' E7 direct injection heavy-duty diesel engine is a four cycle, in-line six cylinder design. The 728 cu in. (12 1) engine is turbocharged and chassis mounted air-to-air aftercooled. The E7 is being introduced in 1989 with power ratings of 250 hp to 400 hp (186 kW to 298 kW) at 1700 to 1800 rpm, calibrated to 1990 EPA standards. Highlights of the E7 engine's design, development and performance are presented. Information is included which illustrates the strategies utilized to attain program goals of controlling weight and cost while extending power ratings, reducing emissions levels, and improving fuel economy, serviceability, durability and reliability.