oil life: how long in months?

[sothpaw]

I was wondering for syn. oil, like mobile 1, how long in months
is an acceptable oil age before an oil change is necessary, regardless of mileage?

I changed the oil Feb 2002 and left it in there. I changed the
oil filter at 3000 mi in Sept 2002. I left the oil and filter in place
over the winter, drove the car last week, and just changed
the oil again. So that oil was 13 months old, with maybe 4500mi
on it.

Is that still reasonable? I'm also a little worried in that the pan
did not fully drain, so I have maybe 1/4 qt or so of 13 month old
syn oil still in there.

[Vettelt193]

A year is the general standard with Mobil 1. The last 1/4 of a quart is impossible to get around. don't worry about it... you can never drain all of the oil. You have done good by changing it. I will suggest doing 3000 mile intervals if you don't drive that often though... It is cheap insurance.