What substance can cause corrosion to components like gaskets and fittings?

Ethanol/gasoline blends are known to cause corrosion in components such as gaskets and fittings due to their chemical composition and the way they interact with materials. Ethanol is hygroscopic, meaning it absorbs moisture from the environment, and this increased water content can lead to corrosion when combined with gasoline. Moreover, ethanol can be aggressive toward certain types of rubber and plastics used in gaskets and fittings, potentially causing them to degrade over time.

In contrast, while lead is toxic and a hazardous material, it does not typically cause corrosion to gaskets and fittings directly. Diesel fuel is less corrosive than ethanol-blended fuels, although it can have its own issues with certain materials under specific conditions. Water can cause corrosion, but it is not a factor in the context of blended fuels in the same way ethanol is. Thus, ethanol/gasoline blends stand out as the primary concern for corrosion among the given substances.