In general, used lubricant oils present heavy metals, which comes from vehicles engine usage. This causes its toxicity to be high in biodegradation periods (Fig. 1, 2 and 3) mainly in tests with E. sativa and E. andrei, despite the fact that oil molecules are more degraded due to the engine’s high temperature and compression levels (Eisentraeger 2002; Lopes and Bidoia 2009). The fact that the chain is more or less degraded does not necessarily mean that the toxicity level is lower. In many cases, the fact that a substance is more degraded makes it more available to soil organisms.