I've heard that changing to synthetic oil would cause a leaky gasket, depending on when you switch. Is this true or a myth? I agree that once you switch over, you should stay with synthetic, but at what cost? Any thoughts on this? What about changing to synthetic tranny oil?

 

Not too sure about the tranny oil but synthetic oil is made to flow into the tiny cracks better then regular oil, especially in gaskets. I think molecularly it can get into places regular oil can't. That's what makes it such a good lubricant. People with higher mileage should be cautious if switching but not all cases will leak though.