PPM calculations

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Sep 6, 2011
I'm using the Lucas engine break in additive. The bottle is 16 oz and which contains 31,000 ppm of ZDDP. When added to 4.5 qt. the zddp content is at 5000 ppm. Now what would the zddp content be (at same rate) in 6 qts.? I have looked up calculations, but I just can't figure this out lol. Thanks for the help!
31000 ppm is 3.1% of a half-quart.
5000 is .5% of 10 half quarts (which includes the original 9 half-qts plus the 1 half-qt of additive)
6 quarts is 13 half-quarts (which includes the half-qt of additive)

How much additive is there?
3.1% of a half-quart is .496 oz of actual ZDDP
.5% of 10 half-quarts is .8oz of actual ZDDP

How much ZDDP is in the oil itself (including the volume of the additive bottle)?
.8-.496 = .304

Therefore, the 10 half-qts contain .304oz of ZDDP (before considering the additive's ZDDP)
Therefore, 13 half-quarts must contain .3952oz of ZDDP (before considering the additive's ZDDP)

How much ZDDP is in 13 half-quarts, in total?
.496+.3952=.8912oz of ZDDP in 13 half-quarts.

Figure out the proportion of ZDDP in 10 and 13 half-quarts, relative to each other
.06855/.08=.856875 (13 has less ZDDP by volume than 10)

The known 5000ppm is reduced by the new proportion

Therefore your 6 quarts (plus additive) has 4284ppm of ZDDP in it.
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What is the original zddp concentration in the 6 quarts of oil?
And is that Phosphorous or Zinc content?

But anyway, assuming the original oil is 800ppm of Phosphorous:

800ppm * 6 qts + 31000 ppm * 0.5 qts = 20300 ppm*qts
20300 ppm*qts / 6.5 qts = 3123 ppm Phosphorous concentration in the final 6.5 quart mixture.

Don't use the whole bottle. That's too much zddp.
4 ounces (0.125 qts) of the additive would give a final concentration of 1400 ppm.
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Just add an oz. or so periodically as the stuff is depleted - you'll feel it and hear it as piston TDC/BDC turn around clatter. You don't need a potentially destructively large initial concentration.
Originally Posted By: SVTCobra
Found on the Lucas oil website that 4.5 qts plus 16 oz of the additive gives 3,500 ppm zinc.

When I originally worked back the 31,000ppm in the pint bottle, that's what I got.

But I figured maybe there was more to it than what the OP posted, so took him at his word for the 5000ppm.


In December, 2007, the publication GM Techlink
, distributed to GM dealers, contained an
article by a GM lubrication guru, Bob Olree,
of the GM Powertrain Fuels and Lubricants
Group. As well as debunking cert
ain other erroneous
ideas about oil, he
addresses the ZDDP
question in detail. In that arti
cle, he flatly calls the concer
n about ZDDP a “myth,” citing the
extensive testing of modern oi
ls for scuff resistance. One pa
ragraph is espe
cially worth
repeating here:
A higher level of ZDDP was good for flat
-tappet valve-train scuffing and wear,
but it turned out that more was not
better. Although break-in scuffing was
reduced by using more phosphorus,
longer-term wear increased when
phosphorus rose above 0.14%. And,
at about 0.20% phosphorus, the ZDDP
started attacking the grain
boundaries in the iron, result
ing in camshaft spalling.

I would not use more than 1400.

At 2000 it is dangerous according to GM Cheers.

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