The world recognizes that the main source of energy used in transportation is diesel fuel because it is more economical and is also more efficient. For this reason, various sectors of transport and fuel production are developing new technologies aiming at the replacement of traditional fossil fuels by other renewable sources. In the current market, it is possible to find systems that run on blends of diesel and other renewable fuels and test systems that run on mixtures of ethanol and some other substance to reduce auto-ignition. To be able to use ethanol in compression ignition (CI) engines where diesel fuel is typically used, the poor flammability of ethanol under compression ignition conditions is the major problem to be overcome. The techniques used in trials with CI engines to correct this problem are preheating the air in the intake manifold, increasing the compression ratio or the addition of an ignition improver for ethanol. In this study, different tests were carried out in a rapid compression machine using ignition improvers derived from polyethylene glycol. Tests were conducted for different instants for the start of injection of the mixtures and different compression ratios.