I can answer the synthetic question, need help!
 

I had my car for three days before I had the oil changed. I checked and rechecked, cold and warm, and I did not have anything leaking from it. Well, I had them put synthetic oil in and guess what?? My car now leaks oil.

My question is: will this hurt anything? What I mean is, if I leave the synthetic oil in and just make sure top it off can I wait a couple months before I go back to regular oil or should I have the oil changed again now? Sorry if this is a dumb question, but I'm a little worried about something I don't know too much about yet. I have a 1986 944 n/a with 93K miles on it.

In my opinion, I would think that it is better to just leave the syn in since you switched. I wouldn't trust putting the regular oil back in.

Due to the smaller size of the molecules in modern synthetic oils, they can find the tiny holes that would cause your current condition of leaking.

A couple of things you can do:
1. Keep using synth oil, but make sure you keep watching your car to make sure you have enough oil. (Not the best soluntion, IMO)
2. Switch back to organic oil, and most likely your leaks will disappear.

In either case, perhaps it's time to replace your seals, including the oil filter / oil tub seals.

-Zoltan.

This is the reason I haven't gone to a synthetic. If you start with a newer engine/seals you probably wouldn't have this problem. Synthetics offer better lubrication due to the smaller and more round molecules. However, the slicker action allows is to slip beyond the older seals. I think as long as the leak is not bad you should stay with the syn. -At least you know which seals need replacing! (BTW, search for posts. This has been discussed before.)

Jeff

Take it out, it's gonna make a mess and get on hoses and belts eventually, and put in diesel grade 15w40 oil.... like Shell Rotella. It's much better than regular gas engine oil and will easily go double the time between oil changes that you are used to.