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Abstract. In this paper, the behavior of different types of biodiesel (from rapeseed, soybean, coconut and palm oils) in contact with different parts of a common rail injection system was evaluated. Stability tests were carried out by static immersion of test pieces in biodiesel at two different temperatures, 50ºC and 75ºC. After 15 days of immersion, interaction between pieces and biodiesel was evaluated considering two parameters: mass variation of pieces and biodiesel acid value (AV). A mass loss in both injector and pipes was found, no matter which biodiesel was used. In case soybean oil biodiesel was used, a slightly lower loss was achieved. On the other hand, coconut oil biodiesel showed a significant acid value increase with respect to the others. The temperature increase influenced mass loss and acid value increase.