You only need to change your Mobil 1 oil every 15,000 miles!

[sperry]

http://neptune.spacebears.com/cars/stories/mobil1.html

Based on the results we've got here, we'd recommend 8,000 miles between oil changes on an engine that uses no oil at all, perhaps 10,000 miles on an engine that uses some oil, and 15,000 miles or beyond with a filter change every 5,000 miles. This, of course, isn't any kind of guarantee, and you must evaluate for yourself what your engine requires. One thing we're pretty sure about though: 3,000-mile intervals is a huge waste of resources.

:shock: Very interesting! I knew that synthetic will last for a while especially if you do filter only changes periodically, but I was amazed that as the oil got older, it actually protected better! I'm about 800 miles overdue right now for a change, I think I'm just going to swap the filter and top it off.

In fact, as Matt (my roommate) just brought up... the very best solution would be to change only 1 quart of oil every 2000 miles or so in order to keep the oil in the post-3000 mile happy zone! Fumoto Valve to the rescue!

[MattR]

We run a special High Grade Chevron Delo Oil in our Diesel's at work, and their service intervals are 25,000!, with a lube every 15000.

I would have total confidence in running a synthetic out to a longer interval.