Correct dilution rate for additive in motor oil

[63Avanti]

Correct dilution rate for additive in motor oil

As I cannot stand watching pro-sports, I do various why-not studies on various topics. One of my current "victims" is oil additives. you already know of the data compilation at http://sterkel.org/avanti/documents/oil_series_for_classic_cars.htm

One question I am running down is:
"how much additive does it take upgrade an oil to a "target" spec."

Here is the "dilution formula" I have:

Oz = (Oil - Target)/(Target - Additive)
where:
Oz: Oz of additive needed to be added to each Oz of oil
Target: the "Target/Desired" wt%/PPM spec
Additive: the additive wt%/PPM spec
Oil: the oil wt%/PPM spec.

I am a little embarrassed as I should be able to work this out myself, but applying this formula does not give me the results I expected.

Corrections definitely appreciated.

 

[TallPaul]

When I run your numbers the result is slightly off and I believe that is because you work with the entire additive ppm. It is easier to subtract out the ppm of the oil from the additive, then everything works much simpler.

Here is one way to do it using only the additive ppm above the amount in the oil:

Pa = proportion of additive you need in crankcase to get the target increase in ppm for the selected parameter (zinc)

Tp(I) = Target ppm increase for zinc

Ap = ppm of zinc in additive

Op = ppm of zinc in oil

Pa = Tp(I)/ (Ap - Op)

Now run this equation:

Total crankcase capacity (ounces) x Pa = Ounces of additive.

Remember the ounces of additive are part of the total crankcase capacity, not on top of it.

Example.

SLOB = 4800 zinc
Maxlife SM = 800 zinc (not exact but easy example)
Suppose we want to raise zinc to 1000 in Maxlife SM. Then,
Tp(I) = 1000 -800 = 200

Pa = Tp(I)/ (Ap - Op)

Pa = 200 / (4800 - 800) = 0.05

On a 200 qt crankcase,

200 x 0.05 = 10 ounces of SLOB

So I would put 10 oz slob and only 190 ounces Maxlife SM in my truck to get a 1000 ppm zinc amount.

I'm sure you can combine these several steps into one grand equation.

 

[63Avanti]

TallPaul,
thanks, I knew that the answer/correction would be embarrassing.

Any chance for this (the right answer) becoming a sticky?

 

[TallPaul]

I wouldn't say embarassing. You just bit off too much to chew at once. You tried to get there in one step. Anyway, your equation, though technically wrong, is close enough for garage mixing work.

If they sticky this we need another equation to calculate the resulting viscosity.

Resulting Viscosity = antilog of the sum of the weighted logs of the viscosities being blended.

On a the above example 10 and 90 percent mix:
V = antilog ( 0.90 log Ov + 0.10 log Av)

Yeah there's a viscosity calculator online, but this is it's equation ad sometimes it's easier to pop out the ol' pocket calculator than to go on line.

 

[63Avanti]

TallPaul,
while you are at it...
...is TBN "additive", namely,
can I use the same formula?
thanks!

 

[TallPaul]

Quote:

---

TallPaul,
while you are at it...
...is TBN "additive", namely,
can I use the same formula?
thanks!

---

Well unfortunately, I am not an expert on oil. I would assume it is additive like zinc since it comes from certain components like zinc and calcium (IIRC), so I assume there is a direct relation between TBN and quantity of TBN supporting/producing/assiciated additives.

In fact ANA Labs told me that the TBN on the CD2 75K stuff made sense in light of the calcium amount.

Anyway, for garage blending, seems a good assumption.