The ISX in Cummins ISX stands for "Inline Six, X-platform." The "Inline Six" refers to the engine's six-cylinder inline configuration, the standard layout for Class 8 heavy-duty trucks. The "X" denotes the platform generation that replaced the older N14 in 2001 (production 2002+). The naming convention runs across the Cummins lineup: ISB for Inline Six, B-platform (medium-duty 6.7 liter); ISC for Inline Six, C-platform (the 8.3 / 8.9 liter variants); ISL for L-platform (8.9 liter), and so on. The "I" prefix was originally added when Cummins introduced electronic fuel injection across the line; pre-electronic versions of the same engines had names like the M11 (predecessor to ISM). When Cummins rebranded the ISX15 to X15 in 2017, the "I" prefix was dropped because every modern Cummins engine is now electronically managed.
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