My guess, 20 years. ----- Original Message ----- From: Dr C A Rubino <rubino at truespeed.ca> To: healeylist <healeys at autox.team.net> Sent: Tue, 23 Apr 2019 13:31:12 -0400 (EDT) Subject: [Healeys] transmission oil had my tranny rebuilt 2 years ago. I run with MT 90 Redline. What is your recommendation regarding when to change the oil?