High strength magnetic steel laminations are the invariable choice to achieve the power density demands of high speed electric machines required in the automotive industry. However, the cost competitive automobile market, favours the use of conventional materials. Consequently, in this paper, a high strength martensitic sleeve rotor configuration is identified as an ideal choice to maximize the use of conventional materials in a high speed synchronous reluctance (SynRel) machine. A 3.5 kW, 60 krpm high speed SynRel machine is designed for an electric assist turbocharger (EAT) to disclose the benefits of sleeve rotor configuration. The performance of the sleeve rotor is on par and superior to a SynRel machines employing high and low strength laminations respectively. Finally, a multiphysics optimization is performed to ascertain the superiority of sleeve rotor SynRel configuration. Based on this, the sleeve rotor produces 4.5% and 46.7% more torque than the SynRel machines using high and low strength laminations with conventional rotor configurations. Additionally, this is achieved with nearly 90% by volume of conventional rotor lamination.