My '83 UrQ has 59k miles on it, and it's been run by the previous owner on 
Castrol Syntec (great oil, BTW) since it was invented, with no problems.  I 
just changed over to Mobil 1 15w-50 synthetic, and have logged about 700 
miles with no problems.  If anything crops up, I'll keep the list posted.
                                                    Regards,
                                                    Tucker Fritch
                                                    '83 UrQ