The aim of this study is to assess how the fuel, through its characteristics, could increase the maximum load achievable in HCCI condition. First a specific procedure has been developed. Second using this procedure, a set of fuels using a Jet B as base fuel and having different cetane numbers (from 33 to 40) and different chemical compositions (via the addition of reactive products which are olefinic and naphtenic compounds) have been tested. We conclude that a fuel having a low cetane number, a high volatility and an appropriate chemical composition could improve the HCCI operating range of more than 30% without a too large decrease of the performance under conventional Diesel combustion mode. (c) 2010 Elsevier Ltd. All rights reserved.