I just wanted to let people know that after I switched from Mobil 1 5w30 to Castrol Edge 5w30 that I perceive the Castrol to be a better oil. My truck runs quieter, the fan is on less and the engine is running cooler. I got 20 MPG with the ECT button on driving up and down a steep canyon twice. I had been getting about 18-19 normal city / highway driving without the ECT button on.
The Castrol Edge is much, much higher in phosphorus and zinc which coat the engine parts and reduce wear.
It is a little bit more money and Wal-Mart doesn't sell it yet here but I feel like I can go at least 7K miles between oil changes. The oil is rated to go 15K or 12 months.
Just thought I might put my 2 cents in and let people know my opinion.

 

Unlike Castrol Edge, Mobil1 publishes product data sheets on every oil they sell. Any person is able to survey these numbers on their website. It comes as the standard oil in more new car motors than any other oil in the world.
Castrol Edge is over priced.