It is now a fairly well established fact that excessive ring and cylinder bore wear can result from the operation of an S. I. engine on neat methanol. The mechanism leading to the excessive wear were investigated using both engine and bench tests.Engine tests using prevaporized superheated methanol indicated that the wear results from reactions between the combustion products and the cast iron cylinder liner, where the presence of liquid methanol in the combustion chamber appears to be an important part of the mechanism. These reactions were investigated using a spinning disc combustor.The spinning disc combustor was used to provide a source of burning methanol droplets which were subsequently quenched on a water-cooled cast iron surface. The condensate formed on the cast iron surface was collected and analyzed for chemical composition. Infrared analysis indicated the presence of large quantities of iron formate, a reaction product of iron and formic acid. Additional spinning disc tests were performed to investigate the effects of surface material on the formation of formic acid.