Miata Mailing List: November 1995, Message #201
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   From: doc.wynne@rodent.isdn.net (Doc Wynne)
Subject: Re: OIL: Doc Wynne
   Date: Fri, 3 Nov 1995 10:18:57 -0500

JS> I found out something interesting about Fram Filters (which I used
  > many times on my 68 Firebirds)... that being... for the Miata,
  > they do not have a CHECK VALVE as the Stock Oil Filters and
  > the Purleator's do.  Just info for your use.

 Thanks for the info. I guess I'll have to go to my dealer and stock up 
on filters.

  >The Dealer: Carlsbad,
  > stated that prolonged use of a non-check valve filter can produce
  > pinging.

 I assume he really meant lifter noise? I cannot seem for the life of 
me to connect pinging to oil filters.  Maybe he was referring to the 
Fram possibly not having a bypass valve? Having a bypass valve would 
allow full oil pressure even if the filter element was clogged, but 
then again, you're now circulating unfiltered oil through the engine. I 
wonder which is worse...low oil pressure with "clean" oil or good 
pressure with dirty oil? (I can't imagine driving so long as to get the 
oil so dirty it'd clog a filter anyway!)

  > He stated that once a car came in.. pinging.. and.. when
  > they put the new oil filter on.. it went away. (I am sure the new  
  > oil change probably worked to help too eh?). 

 No doubt. When I bought my new toy 2 months ago, the dealer told me 
they always did an oil and filter change on any cars before they were 
put out to sell. He was right, but I noticed on the sticker they put in 
10w-40 instead of the recommended 10w-30. It showed on cool mornings...
when started with the engine "cold" but outside temp. above 70 deg. F, 
th oil pressure would top out just shy of 90 psi, dropping to around 60 
once warmed up. On those below 70 mornings, it'd go past 90 upon 
acceleration, but as revs increased, it'd suddenly drop to around 80. 
Once warmed up, around 60 was normal again. This worried me, since I 
figured it was the pressure bypass valve in the oil pump operating. 
Since changing back to 10w-30, it gets the same pressures both cold and 
hot as before, but without the sudden pressure drop when accelerating 
with a cool engine. I feel a bit better about it, anyway.

  Thanks for the tip.

  Doc
  Red 92B
  Team Just Right Oil Pressure

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