Hi, am replacing my oil lines as the lower line is leaking and ready to go soon. I drained engine oil and later loosened lower oil hose fitting from oil cooler and let it drain . . . . I had over a quart of oil drain out. It seems to me that draining the oil cooler each time for an oil change is a good idea given how much oil was actually in the cooler and lower line. This quantity of dirty oil would foul new oil pretty quickly. Fortunately, the threads on my oil cooler fittings were in great shape allowing me to remove lines with little effort. Monday I will take my lines in to a local shop and have new line crimped onto fittings this ending my leaky lower hose saga and creating peace of mind for future road trips. My SD has over 290,000 miles, looks beautiful and still running strong!