Mobil 1 is also the only group IV synthetic oil , castrol and all the rest are group III.

bassicly it means is made out of a higher quality base stock..

Sythetic 5-30 is in NO WAY any thinnner or thicker then 5-30 dino oil... dino oil degrades alot faster and alot of the additives in the oil + the grade of the oil is pretty much gone at 3000 miles. Synthetic has the ability to hold the grade longer over harsher conditions and over a longer mileage frame.