This paper explores the benefits that would be achieved if gasoline marketers produced and offered a higher-octane gasoline to the U.S. consumer market as the standard grade. By raising octane, engine knock constraints are reduced, so that new spark-ignition engines can be designed with higher compression ratios and boost levels. Consequently, engine and vehicle efficiencies are improved thus reducing fuel consumption and greenhouse gas (GHG) emissions for the light-duty vehicle (LDV) fleet over time. The main objective of this paper is to quantify the reduction in fuel consumption and GHG emissions that would result for a given increase in octane number if new vehicles designed to use this higher-octane gasoline are deployed.GT-Power simulations and a literature review are used to determine the relative brake efficiency gain that is possible as compression ratio is increased. Engine-in-vehicle drive-cycle simulations are then performed in Autonomie to determine an effective, on-the-road vehicle efficiency gain. With the possible efficiency gain determined at an individual vehicle level, a fleet model is then used to calculate the aggregate benefit for the LDV fleet. Our simulations indicate that roughly 69% of all LDVs on the road by 2040 will be of this higher-octane variety that uses premium gasoline (98 or 100 RON). Meanwhile, premium gasoline is projected to account for approximately 80% of the total gasoline demand by 2040. Ultimately by redesigning vehicles to take advantage of premium gasoline, fleet fuel consumption and GHG emissions can be reduced by 4.5-6.0% over the baseline case, where no additional higher-octane vehicles are introduced.