Miata Mailing List: May 1993, Message #65
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   From: (none)
Subject: Re: oil pressure and gauge settings
   Date: (none)

Mike Rother  writes:

> A while ago, one participant in this e-mail group expressed concern
> about possible low oil pressure during idle.  I don't recall if that
> person was using the stock, dashboard gauge to assess oil pressure.  In
> any case, I noticed today that the scale on the stock oil-pressure
> gauge is NOT linear.  The scale compresses (gets closer together) at
> higher psi levels.  So, if your oil-pressure needle is pointing at the
> exact half-way point between 0psi and 30psi, the actual oil pressure
> might actually be something like 18psi.  Perhaps the non-linear
> scale contributes to low oil-pressure readings?

	After I had the calibration checked and the pressure read off the
pump I found this out.  It appears to be right at 18psi at the half-way point.
The manual says that 1k warm idle pressure should be 28psi, and the deviation
was what was worrying me.  Replacing the oil pump helped some; I now get better
pressure (nothing below about 18) than I was, but it still isn't what it was
before the dealer did a tune-up and oil change (ominous theme music).  I've
had the good performance place check it again and they said I was getting good
lubrication and not to worry unless it dropped under 10psi.  The owner said
they could shim the pump/valve if I was really concerned about the pressure,
but that he wouldn't really recommend it or do it on his own car (so I didn't).
I just keep an eye on the gauge these days and don't worry about it; with the
temps in the 80s I just enjoy the car!  Perhaps when the redesigned Miatas are
brought out I'll replace mine...

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Michael Garvin - Systems Programmer                       garvin@mmrc.ncsu.edu
Mars Mission Research Center                            (919) 515-5250 [Voice]
North Carolina State University                           (919) 515-7968 [Fax]