Results presented in the article regard the research on a turbocharged dual-fuel CI engine operating on propane. The research indicated that such engine might operate even if 70% of the standard fuel energy is replaced by propane. The research indicated that at such high share of the gaseous fuel, there is necessary to adjust diesel fuel injection parameters but it is important that there is no need to change the engine structure. Injection parameters may be adjusted in a wide range due to the modern fuelling system of the common rail type. The investigated engine was equipped with such system. Adjustments regarding the fuel charge division, fuel charge quantities, and injection timing enabled to influence combustion in such way to obtain its specific parameters, i.e. maximum combustion pressure, rate of pressure rise, maximum pressure, and the burn out ratio similar to those obtained for diesel fuel operation. The obtained results were presented in form of adjustment characteristics of the injection timing of diesel fuel pilot dose for a few chosen values of the boost pressure as well as injection timing of the main dose. The investigations were carried out for three values of the boost pressure, i.e. 200; 400 and 600 [mbar] but also for the naturally aspirated version. Injection timing of the first dose varied in a broad range and depended on the boost pressure. Injection timing of the second dose varied in a narrower range, mainly due to considerable changes in the combustion process. The obtained results answered a number of questions regarding the strategy of selection of diesel fuel injection parameters taking into consideration engine performances as well as combustion at a high share of the gaseous fuel.