I have a 2016 Forester 2.5I Touring with almost 21,000 miles. I'm due for my 30k/30Month Maintenance and my dealer told me that I have to change my differential fluid as part of the maintenance. I checked online and I did not see changing of differential fluid as part of the requirement (2016 Subaru maintenance schedule and new car break-in period). Which should I follow? Thanks.