Changes in fuel composition and the introduction of alternative fuels often create problems of corrosion and degradation in materials. The objective of this research was to determine the resistance of sealing materials in fuels and heating oil with admixtures of biogenic sources such as E10 E85 biodiesel and B10 (heating oil with 10% biodiesel). In pursuit of this aim damage mechanisms of frequently used sealing materials such as FKM (fluorocarbon rubber) FVMQ (methyl-fluoro-silicone rubber) VMQ (methyl-vinyl-silicone rubber) EPDM (ethylene-propylene-diene rubber) CR (chloroprene rubber) CSM (chlorosulfonated polyethylene) IIR (butyl rubber) PA (polyamides) and NBR (acrylonitrile-butadiene rubber) were investigated.The mass tensile strength and breaking elongation of the test specimens were determined before and after exposure for 84days in E85 non-aged and two years aged biodiesel non-aged and oneyear aged B10 and for a comparison in premium-grade fuel at 20°C 40°C and 70°C. The visual examination of some elastomer test specimens clearly showed a large volume increase until break or partial dissolution.The sealing materials FVMQ VMQ and PA were evaluated as resistant in E85 at 20°C and 40°C and a 15% limit in the reduction of tensile properties was determined. None of the examined materials was evaluated as resistant at 70°C with even fluorocarbon rubber losing 20% of its tensile strength in E85.When exposed to biodiesel elastomers were affected in two ways: firstly by absorption of liquid by the elastomers and secondly by dissolution of soluble components from the elastomers in the liquid medium. Swelling resulted from the high absorption by the elastomers CR CSM EPDM IIR and NBR in comparison to their dissolution in non-aged and aged biodiesel. FKM VMQ and PA were evaluated as resistant sealing materials in non-aged biodiesel at 40°C. FKM was still resistant in aged biodiesel at 40°C but only limited at 70°C. The sealing materials CR CSM EPDM and IIR were damaged to a high extent in non-aged and aged B10 as a result of swelling up to 70°C. However FKM was evaluated as resistant in non-aged and aged B10.The exposure tests showed that FKM was the most resistant sealing material in premium-grade gasoline at 70°C whereas the elastomers EPDM NBR CR und IIR even lost 100% of their breaking elongation. The resistance of these elastomers is improved in premium-grade gasoline reducing the temperature to 20°C.