The innovative architecture of the X12 results in a remarkably low engine weight of 862 kg, achieved through a sculptured block design and the use of high-strength composite materials for components such as the oil pan and valve cover.

The X12 is Euro 5 emissions compliant using selective catalytic reduction (SCR) technology with AdBlue/DEF (Diesel Exhaust Fluid) dosing. Significantly, the X12 will achieve Euro 6 compliance without the addition of exhaust gas recirculation (EGR).

The X12 incorporates Cummins' XPI (Extreme Pressure Injection) common rail fuel system, derived from the 15-litre ISX. Generating injection pressures in excess of 30,000 psi, the XPI system improves combustion and fuel economy, reduces noise and enables fast response at low rpm.

The use of a rear geartrain also contributes to overall engine refinement by reducing vibration and lowering noise.

The X12 uses a standard wastegate turbocharger and also has an integrated engine brake that delivers the high retarding power that Cummins heavy-duty engines are renowned for. The engine's single cam in-head design with roller valve train and high efficiency intake ports continues the design theme of minimum complexity and maximum efficiency.