Enabling diesel engines to operate with other fuel can be a solution to reduce the pollution generated by these machines. However, the peculiar physicochemical characteristics of each fuel make it difficult. Ethanol, for example, needs different temperature and pressure parameters to ignite, compared to diesel. The use of reactivity controlled compression ignition (RCCI) engines has been promising to replace diesel fuel partially. In this work was used a single-cylinder IC engine—YAHMAR NSB 50, adapted to operate in RCCI mode, using the strategy of triple direct injection (ethanol–diesel–ethanol) in order to obtain the maximum diesel substitution rate for ethanol. Experimental results show that, operating with the triple fuel injection strategy, RCCI engine showed an increase in efficiency compared to the original engine. In addition, diesel substitution rate for ethanol achieved 72.2%.