I just like changing my own oil. Once I bought a house and finally had a garage again, I jacked up my car and truck and changed out all the oils: rear diff, front diff, transfer case, manual transmissions (the best transmissions) ... it may take longer than just putting into one of those places, but I'm doing it myself and I know I'm doing it right. I can inspect everything and I don't have some kid scanning my VIN number and putting my car into a big marketing and tracking database.