Hello Listers,
According to my collection of repair manuals, The API oil standard in effect
in the early '70s was SE. As best I can determine from the research I have
done, oils rated API SG or SH have the same levels of zinc and phosphorus as
SE rated oils. Anything beyond SH rated will not have the ZDDP needed. I
conclude that an oil rated SG or SH should be OK. Of course, we all know
that the proper viscosity range to use depends on climate, season, and
likely ambient temperatures.
I admit that this approach might be too simple. Oil formulations have
changed over 35 years. Finding reliable data on ZDDP content of oils on the
market today is problematic; I looked through the web sites of all of the
common oil brands I could think of. And many of the oils mentioned in the
numerous threads on the subject are available but not readily obtainable via
retail sources.
My solution: Buy Castrol 4T motorcycle oil at $4.00 per liter. It is rated
SG, SH and I hope is is a good choice.
I will continue to monitor the discussion. One of you may find the perfect
oil for all of us to use. If so, we can enjoy our cars with greater peace of
mind.
Eric
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