The Cummins ISC is a straight-sixdiesel engine, design by a Cummins production line, which is 8.3 litres (506.5 cu in) in displacement. This went into production in March 1998 by Cummins. The engine was built off its predecessor, the Cummins C 8.3 litre engine originally introduced in 1985 as the 6C8.3 (this was co-designed with the Case Corporation, along with the smaller 6B5.9). The first electronic version, known as the C8.3E and designed for the urban bus market exclusively, went into production in late 1996.
The Cummins ISC also has a sister engine which is designed off the existing ISC 8.3 litre cylinder block which runs on compressed natural gas (CNG). Cummins reintroduced this engine as the C PLUS engine which has a maximum power rating of 280 horsepower (209 kW; 284 PS). A few thousand units of this engine engines are now roaming in the world operating on a variety of applications.