[T3] ZDDP: How much is too much?

[Bryon Garvin <spinningrooves@gmail.com>]

I was re-reading some notes I took about the last time I inquired on a ZDDP
additive and also using an oil with ZDDP already in it.  Jim said that the
Lucas product he bought, if used as directed, would bring the ZDDP level to
5000 ppm.  But Jim you said also that you'd probably use the product about 2
oz per oil change and leave it in there, as opposed to draining the system
after 1000 miles like the bottle says.  I also noted that there is sometimes
a warning that too much ZDDP is not a good thing either.  So, how do we know
how much ZDDP to use?

I opted for Valvoline VR1 at my last change which has ZDDP in it.  The only
info I can find on it's ZDDP content is the MSDS which claims the ZINC
ALKYLDITHIOPHOSPHATE level to be 1-1.5% of the quart.  I have a bottle of
the Lucas product that I haven't opened yet.  I'd use the Lucas additive if
the 2 oz at each change will give the proper ppm.  If it's unknown what
using ~2.5q of VR1 contains with regard to ZDDP, maybe I should switch.

Can anyone shed light ?

 - Bryon, '71 Fastback
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