There are several studies that suggest that reusing oil is unhealthy for a number of reasons. Firstly, when you reuse an oil, it simply increases the likelihood of the release of harmful substances. In addition, it also increases the proportion of free radicals in the body which leads to inflammation and several other chronic diseases. However, if there is a need to reuse an oil, it should be for a maximum duration of three times. This is done to avoid the formation of any trans fat. Therefore, you should avoid reusing oil as much as possible. In desperate times, you can reuse oil but only for around three times.