I've got a 1990 Volvo 740 base (non-turbo) with about 132K miles and it's been running on petroleum based oil for quite a while now. I've been doing some reading, and apparently synthetic in my case would be quite good. It gets pretty cold upstate NY near the Albany area, and I'd like to switch. However, I hear that often times after a switch, leaks can show up because 1) the synthetics 'clean' out a leak that some congealed petroleum oil might've been sealing and 2) the synethics get into smaller cracks and can seep out. Has anyone had any experience with this? I know I have a very tiny leak at the moment at the distributor cap, but can someone give me a guestimate of how many leaks I could possibly experience, or what the likelihood is? As in, what are the common ones that show up? And are they costly to repair?

Thanks a lot.