In a move towards fuel efficiency, Ford dropped the M-Series engines (the 5. 8 Liter 351M and 6. 6 Liter 400 cu in V8s) in 1981, replacing them with the 4. 2 Liter 255 C. I. and 5. 8 Liter 351 C. I. Windsor V8 engines from the Panther platform. The 255 V8 was simply a 5. 0L, 302 V8 with a smaller bore, built specifically for better fuel economy, but was dropped for the 1982 model year due to being underpowered and having limited demand. For 1982 and 1983, the 3. 8L, 232 C. I. Essex V6 was the base engine but was quickly dropped for the 1984 model year. In 1983, Ford added Diesel power to the F-Series through a partnership with International Harvester (later Navistar). The 6. 9L, 420 C. I. IDI V8 produced similar power output as the gasoline 351 Windsor V8, with the fuel economy of the 4. 9L, 300 I6. From this point on (1983-present), the heavier duty f-series trucks (F-350 and above) were usually equipped with the Diesel engines as standard horsepower. 1985 was the first year of electronic fuel injection on the 5. 0L V8, all other engines following suit in 1988. There was a new "high output" version of the 5. 8L Windsor beginning in 1984.