Internal corrosion of exhaust systems is of significant interest in the automotive industry. Condensate formation occurs in a muffler at the start of an engine as the hot combustion gas coming from the engine cools down promptly until the temperature of stainless steel of muffler increases above dewpoint temperature of the exhaust gas. Globally there is a certain variety in internal corrosion severity. Since condensate is one of the major factors to cause internal corrosion of a muffler on one hand we have investigated the chemical composition of a number of real condensates in different regions by means of ion chromatography. On the other hand corroded field parts from the same regions were examined by scanning electron microscopy and also their corrosion products were analysed. In addition the impact of a variety of synthetic condensates on the stainless steel material of mufflers was also assessed by immersion tests. In this study the correlation among composition of condensate and corrosion products and the types of corrosion found in the field parts will be discussed.