10lbs per 1k rpm is about what you want. The factory specs oil pressure at 2k rpm. If you're going to low at idle, your engine would probably like a little heavier oil.

Synthetics will not cause any leaks or seapage. The problem already exists if you notice it after the switch. In fact, the seal conditioning provided by synthetics will enhance the sealing properties of gaskets and seals.

Synthetic oil is much cheaper to run. I spend $50-$60 per year for a 5 quart system at 20k miles per year. Which is about half as much as dino oil. Not included, is the longevity of the engine. 200k miles on a synthetic lubed engine is similar to 50k miles with dino oil.

 

Mike, I've had too many guys tell me that when they switched to synthetic oil in their old tired Mustang engines, they leaked where they hadn't leaked before. So, based on testimony, yes synthetic oil will cause an old engine that has been on dino oil all its life to leak in some cases. Not all cases though. It might have something to do with the care of changing the oil at decent intervals in the engine's life.