As the 1980s progressed, fewer private customers purchased the Diplomat, and the M-body was eventually dropped during the 1989 model year. Although sales were strong, Chrysler CEO Lee Iaccoca held a low opinion of the M-body line as a relic of the pre-K car era and declined to invest any money in them. Despite lower gas prices in the mid- to late-1980s and a 2.26:1 rear-end gear ratio, the Diplomat's carbureted engine and lack of an overdrive gear on its TorqueFlite automatic transmission resulted in poor fuel economy compared with its larger competitors from Ford and General Motors, as evidenced by comparing the EPA estimates for 1986 models: