My oil sending unit is the original. I did remove it once. No special socket. I think the base of it is square. I found a wrench that fit it. It's just pipe thread so once it is loose you can unscrew it by hand. I have remoted the sending unit because I installed a T fitting for a marine oil pressure sending switch. I have a large red light on my switch panel to let me know when oil or fuel pressure is low. I have plans to put more things on that alarm light. I used a grease gun hose to remote the oil pressure sending unit. That may be why it has lasted so long. No engine vibration.