Light naphtha is a low boiling point fraction of crude oil, and is ideal for partially premixed combustion (PPC). Sufficient premixing can be realized due to its low boiling point and octane rating (RON = 64.5). This study investigates the combustion characteristics of light naphtha and a multicomponent surrogate under various start of injection (SOI) conditions. In this study, LN and a five component surrogate for LN comprising 43% n-pentane, 12% n-heptane, 10% 2-methylhexane, 25% iso-pentane and 10% cyclo-pentane is tested in a single cylinder optical diesel engine. The transition in combustion homogeneity from CI combustion to homogenized charge compression ignition (HCCI) combustion is compared between LN and its surrogate. The engine experimental results show a good agreement in terms of combustion phasing, ignition delay, start of combustion, in-cylinder pressure and rate of heat release between LN and its surrogate. The low temperature reaction (LTR) phase exhibited by LN and its surrogate are comparable, while ignition delay is prolonged as SOI is advanced from CI to HCCI combustion. Combustion images for LN and its surrogate are almost similar, showing that both these fuels behave the same. The level of stratification estimated from the intensity of images is comparable between LN and its surrogate at various SOI. The stratification analysis shows that combustion is stratified and the decay of stratification is slower for PPC condition when compared to CI condition. Emissions such as NOX, CO and soot concentration are comparable for the real and surrogate fuel. Overall, this study demonstrates that the surrogate resembles its real fuel (LN) under the current set of engine test results.