Decalin, which is promising gas-to-liquid (GTL) fuel through efficient direct conversion from methane, properties appropriate for a diesel fuel. With neat decalin, smoke is remarkably reduced without sacrifice in BSEC in comparison with ordinary diesel fuel when low NOx is maintained by EGR and retarded fuel injection timings. The lower smoke emission with decalin is due to its lower ignitability and higher energy content per unit volume, making it possible to complete fuel injection early in the combustion stage and decrease the quantity of fuel directly injected into hot flame zone. With 20% addition of either cyclohexane or n-hexane to decalin, BSEC and smoke improve while NOx increases slightly. In particular, cyclohexane addition significantly reduces smoke emissions. Compared with ordinary diesel fuel, the trade-offs between smoke and NOx and between BSEC and NOx are remarkably improved with decalin-cyclohexane blends and application of EGR.