For what it's worth I've worked on uncoated concrete floors pretty much my whole life. Painting floors started in the 80's when a bug got put into the publics head that if the shop you went to didn't look like a laboratory you were probably not getting good service. Shops were trying to squash the image of the big,fat guy with the stub cigar and and greasy white t-shirt standing there with big hammer saying "Yeah,I can fix your car". Oil is bad for concrete,I think it even rots it and smells terrible after years of soaking in. You could always tell a shop has been there for a long time by the smell of decomposing oil in the concrete floor. There is a way to combat that,it's called oil dry. The trick is to get it on there as soon as you have a spill. It won't take you long to figure out how to drain oil and coolants with a minimum of spillage using large catch pans but you're always gonna have a little so save your money on epoxy floor finishes and buy more oil dry.I was planning on using a concrete densifier a month or so after it’s poured. Is that too soon? Based on what I’ve read here, I’m not going to use epoxy.
You have been wondering how to heat your shop and I don't know why it didn't hit me right off the bat but one of the reason I quit cars in 06 was because of the EPA and all the BS and fees for waste oil,batteries and coolant. I discovered that if I was a motorcycle,outboard or small engine shop I qualified as a small quantity generator and no longer fell under EPA control AND I could burn the waste oil in a furnace for heat.
I never did,I just stored it in 55 gallon drums and had a waste oil company come pick it up and leave me empty drums to refill. Then all I had to do was keep the proof of receipt from the waste oil company if the EPA pr*k ever came back around.