The objective of this research was to determine the resistance of frequently used sealing materials such as fluorocarbon rubber (FKM), fluorosilicone rubber (FVMQ), silicone rubber (VMQ), ethylene-propylene-diene rubber (EPDM), chloroprene rubber (CR), chlorosulfonated polyethylene (CSM), butyl rubber (IIR), acrylonitrile butadiene rubber (NBR), polyester urethane rubber (PUR) and polyamide (PA) in non-aged/aged biodiesel and heating oil with 10% biodiesel at 20 degrees C, 40 degrees C and 70 degrees C. Mass, tensile properties and shore hardness A/D (for polyamide) of the test specimens were determined before and after the exposure for 84/42 days in the aged and non-aged fuels of different age. Biodiesel fuels are easily oxidized and contain acids and water. The sealing materials: acrylonitrile butadiene rubber, butyl rubber, chloroprene rubber, chlorosulfonated polyethylene and ethylene-propylene-diene rubber and were generally not resistant to biodiesel and heating oil with 10% biodiesel. Fluorocarbon rubber, fluorosilicone rubber and polyamide were the most resistant materials in all tested fuels up to 70 degrees C. The degree of damage to the sealing materials increased with higher test temperatures and the age of the fuels.