Determing how many drain and fills it will take

[mfisher1967]

If my Civic takes 2.5 quarts per drain and fill, and holds a total of 7.3 quarts, how do I calculate the percent of old/new ATF remaining after each drain and fill? This is what I am thinking:

1st drain and fill results in 2.5 quarts of ATF being replaced with new. This works out to 34.5% new ATF and 65.5% old ATF.

2nd drain and fill results in 2.5 quarts of ATF being drained and replaced with new. It is unclear how to account for new ATF from the 1st drain and fill being drained during the 2nd drain and fill.

3rd drain and fill results in 2.5 quarts of ATF being drained and replaced with new. It is unclear how to account for new ATF from the 1st and 2nd drains being drained during the 3rd drain and fill.

 

[mfisher1967]

Never mind, I found the ATF calculator and it will take 4X drain and fill to attain 80% new, 20% old ATF in my vehicle.

 

[Smoky14]

Not really!

 

[Donald]

You need to keep a running number of how many new quarts of fluid are in the AT. On your second change you started with 2.5 QT of new fluid in the AT, but when you drained the fluid you drained .85 QT of new and the rest old, then added 2.5 QT of new so you are at 2.5 - .85 + 2.5 or 4.15 QT of new. The third change you will drain 1.5 QT of new and the rest old, then added 2.5 QT of new so you are at 4.15 - 1.5 + 2.5 or 5.15 QT of new. On the fourth drain you will drain out 1.75 QT of new and the rest old and then added 2.5 QT of new so you are at 5.15 - 1.75 + 2.5 or 5.9 QT of new fluid or 80% new fluid.

But when I drained the pan, I did not get out what was listed in the Amsoil website under capacity. It was less by maybe 1/2 QT.

The tough thing to do when pan capacity is less than 1/2 of total is to get to 90 or 95% new fluid. You are dumping lots of new fluid to get a tiny bit of old. If its synthetic then it gets costly and a flush may be a better answer.

 

[unDummy]

http://theoildrop.server101.com/forums/showflat.php?Cat=0&Board=UBB16&Number=495831

The transmission calculator in the above link is worth saving.

 

[Donald]

The transmission calculator needs to have a space to input cost per QT of ATF, so people can determine if its better to get a flush or a bunch of drain and refills.

 

[unDummy]

Not all maintain vehicles simply based on cost. The calculator is a simple ratio provider.

I also recommend timely drain/refills over eternals flush anyday. If you have a drainplug, cost for a drain/refill is always cheaper then a flush. No calculator is needed.

Flushes also require competent tech's. Many quickee <$100 flushes are not as full as many want to think. The percent varies anywhere from 50-90%.

 

[Donald]

I think timely drain/refills are also a great idea. But how does one switch from normal ATF to synthetic ATF? I contend a flush might be cheaper than many drain/refills in an attempt to get to > 90% synthetic.

I have a competent place to go, but it did take them a 2nd flush (free) two years latter for me to get all Amsoil ATF in the AT. And I had to bring in a 2 1/2 gal. container of Amsoil ATF for each flush. In reality I think they learned something in purging out all of the new ATF fluid in their machine before doing a flush with Amsoil.

 

[1sttruck]

if you have 66% of old atf remaining after a fill, then after two fills it's 0.66 x 0.66, after three fills 0.66^3, etc.

 

[unDummy]

You switch from normal to synthetic ATF over your drain/refills. Unless you're planning on eternal intervals, there is no need to have a complete switch. Just start practicing those timely drain/refills with the synthetic.

If the shop doesn't know how to 'purge' their machine, then I wouldn't call them competent. Looks like they forget to read the flush machine's owners manual.

Nope 1struck, at each drain/refill, you remove some old ATF, some previous new ATF, along with percentages of each previous new ATF. Its a simple formula, but not that simple.

 

[Donald]

Quote:

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if you have 66% of old atf remaining after a fill, then after two fills it's 0.66 x 0.66, after three fills 0.66^3, etc.

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Your math is not correct. The percentage of old/new fluid changes after each drain & refill. You need to use the correct percentage for each drain & refill to calculate things. The math in my example is correct and agrees with the calculator.

While I do lack experience in working on transmissions, I do have a degree in math.

 

[1sttruck]

I might be wrong, I usually fly by and just strafe threads with quick replies full of speling erors and such, but I still think it's that simple.....

2.5 qts new plus 4.8 qts old = 34.2% new = n1

2.5 qts new plus (n1 x 4.8 qts old) =
1 x 2.5 + .342 x 4.8 =
2.5 + 1.64 = 4.14 = 56.8% new = n2

Note that 56.8% new means that there is 43.2% old,
which agrees with my (old ^2) calculation.

2.5 qts new plus (n2 x 4.8 qts old) =
1 x 2.5 + .568 x 4.8 =
2.5 + 2.72 = 5.22 = 71.6% new = n3

Note that 71.6% new means that there is 28.4% old,
which agrees with my (old ^3) calculation.

etc.

 

[unDummy]

Anyone can take a give fill amount and sump capacity and create a formula to work with it or seems to work with it. The spreadsheet works with ANY sump size and ANY fill amount.

 

[Gary Allan]

Quote:

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This works out to 34.5% new ATF and 65.5% old ATF.

---

Real simple. Take the 65.5% and multiply it by 65.5% until you're satisfied with the number (low enough for you). The number of times you have to multiply it (and the results) is the number of fills.

65.5% old fluid left
of that
65.5% of it will be left the next fill leaving
43.5% ..of which 65.5% will be left the next fill leaving
28.5% ..of which 65.5 will be left the next fill leaving
19% ..of which 65.5% will be left the next fill ..leaving
12.6% of which 65.5 will be left the next fill ..leaving
8.25%

Heck, The Critic one time used some real complicated formula on a 50% dilution rate pan drop. That was way to0 simple.

100%
50%
25%
12.5%
6.25
3.2
etc..etc.

 

[XS650]

Quote:

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While I do lack experience in working on transmissions, I do have a degree in math.

---

Yet 1st truck's method was correct. His problem was it was too simple for a mathematician to understand.

If you write the equation focusing on the % old oil left instead of the % new oil, it gets simpler.

 

[Donald]

I still feel one needs to consider two things:

1) How old and ---- is the current fluid, do you want the majority of it out quickly.

2) Are you also looking to move to synthetic fluid?

If you have old ---- fluid, then you either need to do a flush (yourself or have a shop do it), or do do several quick drain & refills using normal ATF.

If you want to convert to synthetic ATF, I think you need to do a flush rather than do it slowly. Dumping expensive ATF via drain & refills does not make too much sense to me. At some point you are dumping expensive ATF as part of a drain & refill to get a little bit more old fluid out.