I remember when I had to remove stains from the concrete floor in our factory, it was just horrible. Nothing wanted to come out. I had already searched on the Internet for ways to do it, but they didn't work. Luckily there are special products for cleaning such surfaces. I found here a list of the best degreaser for oil on concrete https://cleaningproductslab.com/best-concrete-oil-stain-remover/ and it helped me cope with this difficult problem. So I hope this was helpful. Good luck!