This paper first of all summarized the auto-ignition mechanism of high cetane and high octane number fuels from the aspect of chemical reaction kinetics with the main purpose of explaining different auto-ignition characteristics of the two kinds of fuel and providing a classification of fuels with the same ignition principles. High cetane number fuels cover major real compression-ignition internal combustion engine fuels and references fuels in use, including straight-chain alkanes, straight-chain ethers, straight-chain esters and cetane number improvers while high octane number fuels cover major real spark-ignition internal combustion engine fuels and references fuels in use, including hydrogen, carbon monoxide, small molecular alkanes, small molecular ethanol, branched alkanes, cycloalkanes, light olefins, simple aromatic hydrocarbons and gasoline antiknock branched ethers. On this basis, 8 representative high octane number fuels were selected for mixing with the high cetane number fuel n-heptane to study the ignition characteristics of mixed fuels in order to find mechanism and corresponding rules. (C) 2015 Elsevier Ltd. All rights reserved.