100k.....WOW. I remember once I changed my S/C oil 3 times just because...well once was bc I did the coupler and most would just reuse if its not bad but I don't believe in putting used oil back into anything when I can just put new oil in it. It doest hurt to change any oil. You could spend a few bucks on fresh oil or a few thousand for a new motor. 100k miles though, naw i'll pass on that one.