I poured 12 ounces of antifreeze into the engine oil

oil floats on water so if you havn't ran it since this happened, you may be able to just pull drain plug for a few seconds and get most/all of it out that way. if you ran engine it's likely all mixed in with oil. if it sets long enough, like overnight or more, it might settle out again and you can try the above trick. of course officially you should drain, change filter, and put new oil in. then in a day or so, do it again? i mean i've seen high mileage engines run for a week (normal driving) with muddy oil and then changed and no harm done.