Miata Mailing List: September 1993, Message #156
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   From: bruce@lurch.Data-IO.COM
Subject: 5W-30 and synthetic oils
   Date: Mon, 20 Sep 1993 13:54:48 -0400


I have decided to run 5W-XX during the winter, based on the owner's
manual, Miata Magazine, and what people are saying.  I also intend
to run synthetic. 

5W-30 synthetic (Valvoline, Chevron) is hard to find, while 5W-50
synthetic (Pennzoil, Castrol) is pretty common and offered in several
brands.  Is it ok to use 5W-50, or should I go to the trouble of finding
5W-30 synthetic?  What does everyone think?

The oil manufacturer's say that their synthetic 5W-50's
	1. provide rapid oil circulation and good flow at start-up, and 
	2. provide a thick film at high temps for ulitmate wear protection.
They say 5W-50 may be used safely in any application calling for 5W-30.
Their literature suggests that the old disadvantages of overly wide
ranges -- viscosity and thermal breakdown due to the high polymer
content-- do not apply to synthetics.

If it matters, winter temperatures around here rarely fall below 32F. We
will get six or eight days with overnight lows in the mid-upper
twenties, and temperatures in the teens will set records.

--bruce@data-io.com
Monroe, WA