I just bought my wife a new 2015 Subaru Outback and while reading through the maintenance intervals, I see that OCI is now listed at 6000 miles with 0-20 synthetic engine oil. I just traded in a 2014 Outback and the OCI listed for it was 7500 miles. On the last oil change I did on the 14 the oil wasn't even close to being done at 7500 miles based on appearance. Why do you think Subaru has shortened the OCI?