I have to agree on the synthetic will cause leaks being BS! When I changed the oil the first time after I bought the Jetta I used Chevron Delo 5w-40 Full Synthetic oil. Why, because I had most of what I needed on hand from using it in my 6.0 PSD. It holds 15 quarts and doesn't leak/use oil.
The Jetta had a slight drip when I brought it home and it had 15w-40 dino oil. After the switch to synthetic, the drip didn't change. Oh, and the Jetta has 304,000 miles on it. So, the it will cause leaks/leak more is BS!
Also, when I switched the 6.0 over, that didn't leak, didn't magically start.........