I have epoxy flooring in my shop. It has held up extremely well. Prep is EVERYTHING. If that concrete is not ABSOFUCKINLUTELY clean, the paint will peel up. Also, do not dismiss the importance of the acid etching as described in the instructions that come with it. (Mine came with citric acid prep.)
My floor was VERY dirty, but there were no oil spots. I rented a floor buffer and scrubbed it with phosphoric acid, and rinsed many times. I used a shop vac that had a water ejection pump to gather up the copious quantities of water that used and get rid of it efficiently.
When I was done, you could have eaten off of that floor. I made sure the temperature of the concrete and the paint were within the parameters on the instructions. It was winter when I did it, so I had to get it warm, and keep it warm for a while. I put a thermometer on the floor and covered it with insulation to be sure the concrete was warm enough.
The results were excellent. That was 4 1/2 years ago, and the paint is still in nearly perfect condition. The concrete has gotten a few chips from things being dropped. (Not the paint's fault.) A few small spots have peeled, ether from moisture intrusion, (I am below grade,) or places that I patched and did not cure/acid etch the new material adequately. It also shows some wear where my desk chair was.
Oil spills are a snap to clean up. Routine cleaning is with a shop vac, and once a month or so, I wet mop with some Simple Green. It cleans up beautifully.
Moral of the story: Follow the label instructions to the letter. If you think the concrete may not be totally clean, clean it some more.