I thought most people felt that synthetic was OK if you'd recently rebuilt your engine, otherwise use mineral. I've read a lot on the site about this, and it seemed to me that there are concerns about the detergents in synthetics that could lead to leaks in older non-rebuilt engines. I think people also feel that given the lack of zinc in modern oils, oils now developed for diesel cars are recommended. I use such a mineral oil and the car seems happy enough. The other thing people seem to agree on is that you should change your oil often, and ensure you have the dreaded and often missing rubber washer that sits a-top the oil filter when you change it. (I didn't have it, but I do now thanks to the chaps here).
But as Rodd points out, there's a ton of info and more opinions that you can shake a stick out here on the site on this topic. Happy hunting!
JH