Pentosin CHF 7.1 mixing

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Does any know why Pentosin makes such a big deal about not mixing 7.1 with "modern" hydraulic fluids. The web is full of recommendations about not mixing this fluid. Pentosin claims that it is not miscible with other hydraulic fluids. It seems that myths have grown-up around the confusion resulting in many recommendation of NOT mixing CHS 11s with other PSFs and ATFs. I can't find a reason to think that problems will arise from mixing except that the manufacturer says not to do it. Can anyone help me understand the reality of the situation?

Pentosin says no to 7.1 mixing:
http://www.pentosin.net/pressreleases/CRP-116_Pentosin_CHF7-1_V2.pdf

Porsche says 11s is OK to mix (you may have to copy and paste this one):
http://www.google.com/url?sa=t&rct=j&q=4800_1996_640696geolab.pdf&source=web&cd=2&sqi=2&ved=0CCIQFjAB&url=http%3A%2F%2Fwww.pcarworkshop.com%2Fimages%2F3%2F30%2F4800_1996_640696geolab.pdf&ei=drvJTp_bJuOc2AW4_uDhDw&usg=AFQjCNHfMmAyLhWRzpP0APz5Qcf6wzgZTA&cad=rja
 
Originally Posted By: GMorg
Does any know why Pentosin makes such a big deal about not mixing 7.1 with "modern" hydraulic fluids. The web is full of recommendations about not mixing this fluid. Pentosin claims that it is not miscible with other hydraulic fluids. It seems that myths have grown-up around the confusion resulting in many recommendation of NOT mixing CHS 11s with other PSFs and ATFs.


The most plausible explanation I've heard is that it's not so much a problem of miscibility, but with what other fluids would do to the seals of systems speced for the 7.1. Apparently, the Pentosin can be mixed with other fluids with the same specification (I believe Bilstein makes one, offhand), since that would be safe for the seals.
 
According to Pentosin, CHF 11s can be used in systems that spec CHF 7.1. However they recommend that the system be flushed of 7.1. So, the seals in these systems can tolerate 7.1 and they can tolerate 11s. But, Pentosin suggests that they cannot be mixed. So, why would the seals be able to handle either fluid, but not a mixture of the two fluids. I still don't understand this one.

I am curious if there is some sort of additive incompatibility or an additive in 7.1 that will not stay in solution a particular synthetic base fluid found in more modern hydraulic fluids.

I don't think that the seals are the problem, but I am prepared to corrected.
 
Okay, you got me now. I'm out of ideas on that one. I thought you were referring more to say, topping up with generic PS fluid, when a system specified 7.1 or 11s, not about switching to 11s from 7.1. That's a good question.
 
I have heard/read both not to mix and mixing is ok for 7S and 11S, so am also interested if anyone has any real insight into this question. In practice, I top off (also turkey baster method flush through the ps reservoir) all the VAG products I maintain with 11S, and assume most have had 7S installed from the factory. No problems to date.
 
Have we found a limit to BITOG knowledge? I was not surprised when I had limited responses to VersTrak fluid questions (it is manufacturer specific with no aftermarket alternatives in many applications). However, I thought that someone would just rattle off an authoritative response on this question.

I suppose that this question is similar to one related to ATF in GM power steering. (GM recommends PSF instead of ATF.) We all know the legends, we just don't know if they are true or myths.
 
Originally Posted By: zanzabar
In practice, I top off (also turkey baster method flush through the ps reservoir) all the VAG products I maintain with 11S, and assume most have had 7S installed from the factory.


I used a "better" flushing method on my old Audi. A seal went in the pump, so I had to keep topping up with Pentosin until a seal kit was shipped to me. At $30 per quart, I wasn't happy. At least the seal kit was under $5.
 
Originally Posted By: Whitewolf
Would anyone like to bring CHS 202 into this discussion?


Ok, I'm in for a discussion that involves all three - CHF 7.1, 11s and 202s. They're remarkably similar. They all do the same job, their physical characteristics differ in the third significant digit, and they're relatively expensive.

So what are the differences, other than that 7.1 doesn't play nice with the other two if mixed?
 
I would be more than happy to discuss all three, but I clearly don't know enough to discuss the two that started the thread.
 
Originally Posted By: GMorg
Everyone shouldn't jump in at once...


I exhausted my theories and knowledge on the issue already.
wink.gif
 
I can add that 11s is primarily a di-alpha-olefin (decene dimer <75%). 202 is less than 20% decene dimer. 7.1 is about 50% hydrotreated middle distillate with 2.5% ZDDP, (no decene is listed). 202 and 11s do not list any ZDDP on the MSDS.
 
In an attempt to find a better PSF, I found a document related to this thread and thought I could provide an update. I found an older pds for CHS 7.1 that states that "additives" used in 7.1 are not miscible with "modern..fluids" such as 202 and 11s. However, the language used in the document is less than perfect. It may be that the pdf was created by an automated translator.

I still can't get my mind around what sort of additive would be soluble in 7.1, but would not be soluble in other PSFs.

If you use the link below, copy it and paste into your browser. The spaces in the file name do not appear to be compatible with this site's software.

http://members.rennlist.com/jandreas/Pentosin CHF 7-1_V1_GB_.pdf
 
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Resurrecting this; personally I think it almost "has" to be the ZDDP additive pack in 7.1, since 11S and 202 seem to rely on uber-basestocks and almost no additive pack to do their job. 11s and 202 aren't formulated to keep a ZDDP additive pack in suspension, and that is bad.
 
This is the first time I have seen this thread but you will notice the 7.1 is a mineral oil based fluid and has a high viscosity index, most likely due to a high dose of a specific VII such as an Olefin Copolymer (OCP).

It is possible they found that this OCP was not not compatible with some esters and or PAOs found in full synthetic hydraulic oils.

I have discovered that certain Olefin Copolymers are not miscible with certain types of fluid mixes, so I try to avoid those OCPs.

The problem I found was these OCPs is that they did not want to disperse in the host fluid, even with a good dose of dispersant. The OCP tended to clump in small globules and would even stick to the sides of the containers.
 
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CHF 7.1 MSDS states:

Distillates (petroleum), hydrotreated middle 25-50% CAS#64742-46-7

CAS#64742-46-7 has trade names of Amoco NT-45 process oil and Kermac 600W (mineral seal oil)

also has 2.5% by weight of ZDDP.

What could make up the other 47.5-72.5% of this by weight???
 
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