Sixteen automotive elastomers were investigated in the methanol/gasoline system. The results show that although few elastomers are affected drastically by pure gasoline (e.g., natural rubber) and few by the pure methanol (e.g., Viton), most of the elastomers are severely affected by mixtures of the gasoline and methanol rather than the pure components. Results on the ethanol/gasoline system are similar to those of methanol except that the ethanol mixtures have slightly less severe effects. Only in the case of Viton a greatly reduced effect in the ethanol system was observed.In comparing the results of the different elastomers it was found that several of them swell less and retain more of the tensile strength after aging in alcohol/gasoline mixtures than nitrile. These elastomers include fluorocarbon elastomers (Viton), fluorosilicone, polysulfide, F-70A polyether, polyepichlorohydrin homopolymer, and polyester urethane.