Engine Oil Discussion
this will do the job
Olio Hot Rod & Classic 10W/30 10679 - Promorally
the zinc has nothing to do with leaded petrol or lack of lead in unleaded petrol
its a a compound that chemically bonds to iron surfaces so it acts a a chemical barrier between the cam lobe and the cam lifter in addition to the oil.
i.e it helps avoid disasterously quick ware and damage when metal to metal contact could occur (i.e it doesn't occur when ZDDP has bonded to the surfaces)
don't just put 10w30 from your local mobil/bp/shell/chevron/texico filling station
the zinc compound is not included in great enough quantities in modern oil, used in modern cars, because it isn't necessary with roller lifter/cams and it probably damages catalytic converters.
mineral or synthetic oil?
Up to you, one costs a lot more and i'd save that expense for my rebuilt engine
keep in mind oil technology has changed dramatically over the 50 years your car has existed
so the 10w30 you buy today will be much better at its job than the 10W30 the first owner purchased back in 1974 and they would probably not be using synthetic oil in a Valiant back then.
change the oil filter as well
Dave
