Miata Mailing List: May 1994, Message #109
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   From: tom.manson@pobox.com (Tom Manson)
Subject: Re: Oil Changes/Pressure/Washers
   Date: Thu, 5 May 1994 22:04:58 -0400

Miateers,
I did my first oil change on Mimi (up to now I had had it done
by a garage).  I used 5W30 oil and Bosch oil filter and purchased a half
dozen washers from the local dealership.

I have several comments and questions stemming from this oil change.

First, I thought that it was tremendously easy to get to the filter.
After all the different methods explained, I thought that it would be
much more difficult.  I just reached down from above the intake manifold
and unscrewed it.  What had been installed previously was a Fram brand
filter.

When I pulled the plug is was accompanied by a "strange" washer.  The
washer had a thin metal body (about half the thickness of the aluminum
ones from the dealer), and on the inside diameter was what appeared to
be a rubber insert (probably as thick as the aluminum types).  There had
been no evidence of leakage and fit the plug very well.  I decided to
leave it on as a trial basis rather than replacing it with one of the
compression-aluminum one.  I'll check it in a couple more days to look
for any evidence of leakage.

The Bosch oil filter has a visible spring inside its bore.  Perhaps what
has been referred to as a check valve (I actually think that it is the
over-pressure relief in case of clogged filter pores).  The Fram that I
removed didn't have such a spring visible, but did have some sort of
short, fat, cylindrical mass at about the same location.

What bothers me is that the oil pressure is now running significantly
higher during warm-up and I believe just slightly higher during warm
operation.  Has anyone changed to Bosch filters and noticed this
pressure increase?  I am tempted to go get another Fram and put it on to
verify that it is the filter characteristic.

Comments?
Tom Manson
Tom.Manson@pobox.com
Manson@fsd.com