Miata Mailing List: May 1993, Message #13
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   From: (none)
Subject: Re: Oil
   Date: (none)

> There's been a lot of discussion on oil weights lately.  I happen to be
> down getting an oil filter this weekend at the local Mazda dealer.  While
> I was there, I asked to look at the official Mazda workshop manual.  It was
> for the 1990 model (nothing's changed in later years concerning oil).  It
> had the usual chart for oil weight and temperature.  It said that for above
> 80 degrees F, you should use 10w40 or 50 (50 especially above 100 degree
> F).  The mechanics were unaware of this until I pointed it out to them. 
> They said they always put in 5w30 no matter what time of year.  It sounds
> like they're being cheap and lazy.

perhaps.
the "recommended oil temperature range" charts have been pretty much
the same for years, no matter what the car is.  i doubt you can go
too far wrong if you stick to the chart.
that doesn't mean you have to change oil grades immediately if you
get one 80+ degree day out of the month, but if you regularly exceed
the top temperature in a given oil grade range, then you should probably
be using something that fits the chart.  if you regularly have 100+
temperatures, you need to allow for that.

so: if the local dealer unconditionally ignores the charts, i'd say
"yes, they're probably being lazy and/or just plain stupid."
if in doubt, perhaps you should speak to the service manager about
their oil policy to help you decide if you want to continue going to
that service dept. or not...

> Have the official Mazda factory recommendations changed?  30 weight oil
> seems mighty thin out here in the desert in summer (100+ degrees).

according to the latest Miata Magazine (p.23) "Mazda has recently advised
Miata owners to use 5W-30 weight oil in their cars.  This is response to
the number of complaints of hydraulic lifters taking a few seconds to
"pump up" after a cold start.  If you are having no such symptoms with
10W-30 oil, stick with what you've been using.  If you hear top-end
ticking upon start-up, switch to the 5W-30 oil."

i think it's reasonable to say (as the MCA says) that if you don't have
a problem, don't change anything.

at the same time, i think the temperature charts win - if the temp.
is outside the range of 10W-30 (or 5W-30, whichever you're using),
change to an oil that can handle those temperatures...