I put some chicken/beef into my slow-cooker, pour some olive oil and cook it for 4-5 hours. After that, if some meat is still left in the cooker, I may heat it up again the next day or the day after the next day, etc. Then, when all meat is finished, I just throw away the oil & meat juices from the cooker but don't wash the cooker with water. I put new raw meat, pour some fresh olive oil and repeat again the cooking process. Is it bad that some residues of the old olive oil from the previous cookings are present in my new cookings? Is there carcinogenic stuff in the old oil?

  • Is there anything burnt / stuck in it?
    – Luciano
    Sep 10, 2019 at 11:44
  • 4
    At some point, just clean it... Whether or not there are some "carcinogenic" in it.
    – Max
    Sep 10, 2019 at 12:39
  • With an iodine number of 75 to 94, I treat olive oil as a semi drying oil. en.wikipedia.org/wiki/Olive_oil That means you should clean it out maybe a couple times a year. Good thing you are not using corn oil. Sep 12, 2019 at 23:56

1 Answer 1


You have a couple of potential issues, one possibly dangerous, the other has to do with flavor/quality control. First, by not washing your cooking vessel, you leave the potential for bacterial growth. This would be especially true if there is some down time (even a couple of hours) between uses. The quality issue is that over time residual oil is going to become rancid, introducing off flavors into your food products. So, I would strongly suggest a wash in warm, soapy water, or the dishwasher, between uses.

  • 1
    Very mild statement of truth. I find the whole concept so horrifying I'm totally speechless
    – user57361
    Sep 13, 2019 at 0:36

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