Burning methanol produces formic acid, which can cause steel corrosion at temperatures below the dew point of the exhaust gas. Because of the potential of methanol as an alternate automotive fuel, it is of interest to evaluate the conditions, which can aggravate or mitigate the extent of this rust formation. Rust formation is promoted by such methanol contaminants, as organic chloride and peroxide. The effects of these species on rust formation were measured quantitatively as a function of concentration by the application of burning methanol in a simple, novel coupon test. Rust formation can be inhibited by cofuels or by lubricants. Effects of Indolene Clear and of other methanol cofuels were measured by the coupon test as a function of concentration. Corrosion protection by engine oil was evaluated as a function of acid-neutralizer concentration and layer thickness. Conclusions about the relative importance of corrosion modifiers are based on gravimetric, spectroscopic and microscopic observations.