In-cylinder blending of gasoline and diesel to achieve reactivity controlled compression ignition (RCCI) has been shown to reduce NOX and PM emissions while maintaining or improving brake thermal efficiency as compared to conventional diesel combustion (CDC). The RCCI concept has an advantage over many advanced combustion strategies in that the fuel reactivity can be tailored to the engine speed and load allowing stable low-temperature combustion to be extended over more of the light-duty drive cycle load range. However, the current range of the experimental RCCI engine map investigated here does not allow for RCCI operation over the entirety of some drive cycles and may require a multi-mode strategy where the engine switches from RCCI to CDC when speed and load fall outside of the RCCI range. The potential for RCCI to reduce drive cycle fuel economy and emissions is explored here by simulating the fuel economy and emissions for a multi-mode RCCI-enabled vehicle operating over a variety of U.S. drive cycles using experimental engine maps for multi-mode RCCI with E30 and ULSD, CDC and a variety of 2009 port-fuel injected (PFI) gasoline engines ranging from 1.8L to 4.0L. Simulations are completed assuming a conventional mid-size passenger vehicle with an automatic transmission that is optimized for each engine. RCCI fuel economy simulation results are compared to the same vehicle powered by a representative 2009 PFI gasoline engine over multiple drive cycles and showing at least a 20% improvement in fuel economy over a PFI baseline. Engine-out drive cycle emissions are compared to CDC and observations regarding relative gasoline and diesel tank sizes needed for the various drive cycles are also summarized.