Why Mobil 1? It's freakin awesome.

Here is a synopsis of the Mobil 1 Test Results done by the
Paradise Garage

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

Mobil 1 5W30 Super-Syn Formula

Down the hatch! Our LS1 gets its Mobil 1.

Mobil 1 currently enjoys the distinction of being the only readily available true PAO synthetic motor oil. You can get the stuff at Wal-Mart for Pete's sake! Perhaps because of its wide availability and comparatively low price, we entered this test with both hope and skepticism: hope that it would do well and vindicate millions of M1 users, and skepticism that it would pull it off. We were expecting it to look pretty beat up by 8,000 miles or so; to say we missed the mark would be polite understatement. Mobil 1 really delivered: 18,000 miles later, it was showing its age but was still hard at work protecting the engine.

As our first phase of the Synthetic Oil Life Study, it was as much a learning experience for the process as it was for the results. We changed some things along the way -- moved the filter change from a mileage-based rule to a performance-based rule, altered the tolerable limits for viscosity, learned a lot about TBN, and a few other things -- which set precedents for the remainder of the study.

But the big question is, what have we learned so far? Here are a few points to ponder, based on our experience with the Mobil 1 phase.

Engine wear actually decreases as oil ages. This has also been substantiated in testing conducted by Ford Motor Co. and ConocoPhillips, and reported in SAE Technical Paper 2003-01-3119. What this means is that compulsive oil changers are actually causing more engine wear than the people who let their engine's oil get some age on it.

Topping up the crankcase is a critical component of extended oil change intervals, and frequent filter changes are most likely the key to extreme-length intervals. The cumulative effect of even minor top-ups, let alone a filter change, substantially increases the longevity of the oil.
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.

The Effect of Top-Up Oil
The Mobil 1 oil in this test indisputably ran for 18,000 miles; 12,000 miles without a filter change.

Some would point out, though, that the make-up oil along the way skewed the numbers. This is a valid point, and the effect is cumulative across the test, especially after the filter change. Fortunately, we know the quantity of oil we added, so conjuring up a hypothetical "corrected" oil age, based on the effect of refreshing the oil periodically, is simply a matter of tedious mathematics. This corrected oil age assumes zero oil consumption -- something that few if any engines can match, especially over 18,000 road miles -- so for most engines the truth will be somewhere in between. For us, the corrected oil age is 10,300 miles.

Indeed, the filter change at 12,000 miles refreshed the oil so well that its corrected age actually remained below the 12k sample's corrected age for almost 3,000 miles! It's no wonder extended-use oil change schemes demand frequent filter changes. The top-up that follows the fresh filter is practically a time machine for your oil.