The X90 is powered by a 1.5 litre three-cylinder turbocharged GDI engine, similar to that on the X50 Flagship as well as the newer X70 models, but with the addition of a 48V mild-hybrid system.

The inclusion of the mild-hybrid system has bumped output numbers up, with the 190 PS and 300 Nm on tap being 13 PS and 45 Nm more than the 177 PS and 255 Nm on the 1.5 TGDI without the BSG. Aside from more power and torque, the company says that mild hybrid boosted powertrain improves standing start acceleration by up to 10%, passing acceleration by up to 15% and reduces CO2 emissions by up to 13% compared to the 1.5 litre engine in the base X70.