Mine was not bad at all the first time I did it at 50,000 miles but I did it again at 60,000 just for good maintenance. It is totally normal to be dark and smelly. It is NOT normal to be the consistency of tar, lumpy, full of metallic bits or more than maybe 1/8 inch below the fill plug. Mine actually began dripping out when I removed the plug and I had the car perfectly level. It only holds 18 ounces so if it is low, problems will occur.