pentosin substitutes revisited - conclusions

[Livolsi, Stephane]

What I wanted to find out was:

> why is the Audi spec'd fluid SO expensive?
> Is it REALLY that different?
> WHAT makes it special?
>
> In the process I have learnt a lot about hydraulic systems and oils in
> general.  Even if I don't find the "Shangri La of hydraulic fluids" I am
> better for the experience as I have educated myself.
>
>
>
> Audi specified certain qualities for the hydraulic oil for their systems
> based on the requirements of the system components built by ZF, Girling
> and others. Pentosin created the product.  We'll just talk about the
> original CHF 7.1 to keep it simple.
> Audi spec'd a fluid that is mineral based, with a density of .84 @ 20C,
> flash point of 130C, Pour point greater than -60C, a viscosity index of
> 340 (which means it will not change viscosity much over a given temp
> range, as I found out thanks to other listers) , viscosity of less than
> 1100 @ -40C, 18 @ 40C and 6 @ 100C.  (this info is taken from the Pentosin
> website)  They labeled this product G002000.
>
> You must agree that you don't need G002000.  You need an oil that is
> mineral based, with a density of .84 @ 20C, flash point of 130C, Pour
> point greater than -60C, a viscosity index of 340, viscosity of less than
> 1100 @ -40C, 18 @ 40C and 6 @ 100C.
>
Those viscosity figures now make sense to me, thanks to info from the web
and listers.

> In my research I found that virtually all oil manufacturers cross
> reference the spec's on their products, to the spec's from other
> manufacturers.  For example Mobil XXXNNN meets or exceeds the requirements
> of Caterpillar NNXXXNN.  Hence they are interchangeable.  Caterpillar
> tells you to use only product CAT NNXXXNN, but there would be no harm in
> using Mobil XXXNNN because they are the same thing.
>
> I did not find 1 single manufacturer who cross referenced to G002000.
> Maybe I should have stopped right there, but I didn't as I was curious.
>
> The 'magic' of G002000 appears to be the viscosity index which indicates
> the effect of temperature change on the viscosity of a fluid.  My
> understanding is that a higher viscosity index (VI) indicates a fluid
> whose viscosity changes less over a temperature range.  Higher number is
> good, lower number is bad.  CH 7.1 has a VI of 340 so this is our
> benchmark and likely why no other oils "meet or exceed" the specs of
> G002000 (at least no oils that I have found yet).  Apparently the
> engineers at Pentosin managed to reduce the effect of temperature on their
> hydraulic oil whereas other companies either haven't bothered, or haven't
> yet figured it out.
>
WRT to the Mobil DTE specifically, there should be no problem whatsoever for
those in moderate climates, but those of us in the great white north (on
both sides of the pond) shouldn't use it because it will damage the system
components over time.  The high viscosity at low temps will likely starve
the pump and or create cavitation, both of which are very harmful.

There are other hydraulic oils out there that meet all the other spec's of
CHF 7.1 and 11S except for the viscosity index so you could use them
seasonally - probably ATF in summer and a winter hydraulic fluid.  Generally
these would be unacceptable because if you are using a winter hydraulic
fluid, it likely will become too thin as the engine bay heats up.  This will
result in damage due to lack of proper lubrication.

Thanks for reading and thanks to those who gave input and information.  And
fix the leaks and stick with the G002000.

> Stephane
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