Biodiesel is a natural solvent, and it can eat through rubber rings and connectors in an engine. While fuel mixtures that are low in biodiesel are not likely to cause significant corrosion (though corrosion can still occur), corrosion can occur relatively quickly with the use of mixtures that are high in biodiesel. Facilities managers that are using such mixtures may need to replace rubber fittings with stainless steel.
Biodiesel will also eat rust that forms on the inside of a fuel tank when condensation occurs. Though this keeps the fuel tank rust free, sediment can accumulate in the fuel, which can cause engine damage. To prevent the accumulation of sediment, rust should be treated with an algaecide or rust remover when the tank is empty. If rust is removed during every fuel change, it is not likely that enough will accumulate to cause sediment in the fuel.