Conventional fossil fuels are more and more regulated in terms of both engine-out emissions and fuel consumption. Moreover, oil price and political instabilities in oil-producer countries are pushing towards the use of alternative fuels compatible with the existing units. N-butanol is an attractive candidate as conventional gasoline replacement, given its ease of production from bio-mass and key physico-chemical properties similar to their gasoline counterpart. The compared combustion behavior of gasoline and n-butanol is tested on a single-cylinder direct-injection spark-ignition (DISI) unit with optically accessible flat piston. The analysis is carried out at stoichiometric undiluted condition, lean-diluted and EGR-diluted mixture for both pure fuels. Numerical simulations are presented on the same set of operations and a dedicated set of detailed chemistry simulations are carried out to accurately predict laminar flame speed for both gasoline and n-butanol at selected engine-relevant conditions. Moreover, a method to accurately fit target results is presented and it is applied to obtain a fitting polynomial form of laminar flame speed for both fuels. Mixture preparation and combustion development are carefully analyzed to explain the experimental evidence and to argument the differences between the two fuels, as well as the fuel-specific tolerance to mixture leaning and EGR-enrichment. Finally, conclusions are drawn to summarize the obtained results and to outline the foreseen advantages of using n-butanol as gasoline substitute in modern SI engines.