what type of oil is best...?

ive got a ss2 jap import celica,1994 it says mineral oil part sythetic but i can only find shitty halfords stuff any ideas guys....?want the best for the best protection.
also addative slick 50 yes or no....?
cheers
2fast2celica

Here's a thousand opinions:
http://theoildrop.server101.com/cgi/ultimatebb.cgi

i know alot of people go for full synthetic royal purple, expensive but good