Incorrect discard of oil used by fishing ship in the brazilian north region has become a common activity. Despite the possible hazard to the aquatic organisms, still missing scientific data about their toxicity. Thus, this study aimed to evaluate the stress and lethality caused by lubricant oil (FSAOLU) on fish Hyphessobrycon eques. Therefore, it was used six different concentration diluted in water (0, 22, 24, 26, 28, 30 and 32% of oil) and three replaces during 96 hours. At the end or during the experiment (with dying fish), it was collected blood samples (cutting the caudal fin) to determine physiological changes. The FSAOLU showed mean lethal dose (LD50-96h) of 27.36%, classified as toxic causing alterations in glucose values from the 26%. The greater dilution of FSAOLU (32%) increased 115% in glucose values when compared to the control. Thus, lubricant oil when discarded in water, it present hazard to the aquatic organisms causing stress and mortality for fish being necessary adequate management to discard of this residue.