Synthetic vs. Dino oil has been debated since synthetic existed. Lots of guys on the Diesel forums swear by synthetic and do extended oil changes.
The main advantage is it has a wider viscosity range (called viscosity index in the trade) than Dino oil. Where you can get say 5W-30 or 15W-40 in Dino, you can get 0W30 or 5W-40 in Syn
The myth about synthetic leaking more than Dino oil is just that -- a myth.
Like Jerry said, you might as well flush the money you'd spend on Syn oil.
