Mineral Oil as Hyd Fluid

Bernie Benz b.benz at charter.net
Tue Jul 29 09:28:43 EDT 2003

As long as we are in the blu sky of sheer speculation, I wouldn't touch the
stuff, unless a diaretic was in order.  Engine oil would be a better
substitute, at least it has lubricating properties.  Currently, I'm using
tractor hyd oil.  But a stupid thread, let's drop it.


> From: Phil and Judy Rose <pjrose at frontiernet.net>
> Date: Tue, 29 Jul 2003 11:05:58 -0400
> To: Steve Sherman <spsherm at attglobal.net>
> Cc: 20v <200q20v at audifans.com>
> Subject: Re: Mineral Oil as Hyd Fluid
> At 10:40 PM -0600 7/28/03, Steve Sherman wrote:
>> As a tangent to my other post about my hyd fluid leak, I am curious to
>> get the lit's opinion on the emergency use of mineral oil (the type you
>> buy in the drug store) as a substitute for the proper stuff.  I did not
>> need it, but did pick up a bottle at a drug store in case the fluid loss
>> became severe and I needed it to get home.
>> What's the deal with the drug store mineral oil?  Is it safe to put it
>> into the hyd system?  Will it eat up seals, ruin the other fluid, etc?
>> Be good to know if this stuff can be used in emergencies...
> Interesting question, considering that mere (hah) substitution of
> Pentosin-7 in place of -11S generates much debate on these lists.
> If you (or I) happen to be caught out in the middle of nowhere with
> no hydr. fluid available except from the drugstore, and if what stood
> in the way of returning to civilization was simply a few ounces of
> hydraulic fluid, I might consider taking the risk of adding some of
> that drugstore mineral oil in order to do a limited amount of
> driving. However--assuming the drugstore stuff would even have a
> fairly similar viscosity to Pentosin (note that USP mineral oils can
> range widely in viscosity)--it is very likely to have a _much_ higher
> "pour point"--a bad thing--which could render it unusable in winter
> (i.e., for cold starting). Also the drugstore stuff's "flash point"
> will likely be significantly lower than Pentosin, so more risk of
> combustion. Bottom line (IMHO) seems to be--if you can avoid using
> very much of it (a few ounces at most), avoid temperature extremes,
> avoid bad luck and avoid extensive driving--you and your hydraulic
> system might survive the experiment. But why (experiment)? Why not
> pick up a liter of Pentosin to use in an emergency you can well
> anticipate--and eliminate all the doubt, uncertainty and risk of
> damaging many hundred $$$ of car parts (to say nothing of the car
> itself)?
> As to ruining the seals--possibly--although the drugstore stuff is
> likely to be pretty compatible (chemically); it could conceivably
> cause the seals to swell more than Pentosin does (and for all we know
> it could also cause the seals to shrink). As to "ruin the other
> fluid"--assuming Pentosin properties are optimized for this system,
> replacing a significant proportion will certainly leave you with a
> "sub-optimal" fluid. Does that "ruin" it? Yes, IMHO. Although if you
> live/drive only in moderate temps, you might get away with it for
> quite some time.
> Phil
> --
> *********************************
> *  Phil & Judy Rose           Rochester, NY  *
> *        mailto:pjrose at frontiernet.net       *
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