| [GMCnet] Synthetic oil. Just some thoughts [message #282313] |
Fri, 17 July 2015 10:34  |
fbhtxak
Messages: 191
Registered: April 2006
Karma:
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Senior Member |
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Bob,
Well stated.
Relevant reports by Blackstone Labs:
http://www.blackstone-labs.com/which-oil-to-use.php
http://www.blackstone-labs.com/search.php?Keywords=ZDDWhat
Note their observations on (1) oil brands (i.e., buy on the basis of API
certification, not brand) and (2) "ZDDP". On the latter, for my GMCMh, I use
the latest API spec for dino oils without regard to ZDDP levels and I buy
"at market". Based on Blackstone lab reports on samples I have sent them
over the years, there has been no change in the rate of wear as ZDDP levels
have diminished. Further, there has been no discernible change in the
overall performance of the "403" in my '78 Royale over the past 22 years and
about 100K mi. (I bought it at 25k mi.). I have, however, meticulously
maintained the engine (and other aspects of the motorhome) at the specified
intervals for all services.
I use synthetic lubes only as specified by the manufacturers for vehicles in
my "fleet". Machines designed for use of synthetic lubes have much tighter
clearances and operate at higher temperatures than "old technology"
machines. Use of dino lubes in machinery designed for synthetic lubes will
greatly shorten service life. Alternatively, there is no evidence that the
service life of "old technology" engines (and other machinery) is extended
from the use of costly synthetic lubes.
'Regards,
Fred
Fred B. Hudspeth
1978 Royale - Tyler, TX
1982 Airstream Excella 28' Mh - Cooper Landing, Alaska
Message: 6
Date: Fri, 17 Jul 2015 01:21:15 -0500
From: Bob Dunahugh
To: "gmclist@list.gmcnet.org"
Subject: Re: [GMCnet] Synthetic oil. Just some thoughts
Message-ID:
Content-Type: text/plain; charset="iso-8859-1"
Dennis Sexton brought up cold starts. Outstanding topic. In 1970 when I was
attending the University of Northern Iowa. A classmate was doing a study on
oil filters. And when the oil filter bypass valve had to pass oil for proper
engine lubrication. ( And I'd love to remember his name ) He was only
working with GM engines. Cold starts were a point of interest. So we used a
Corvair engine to observe oil movement in a crankcase. So I striped a
Corvair engine down to the bare minimum. Then replaced the engine block top
block cover with a plexiglass cover. In this way we had a way to see how
oil moved in a crankcase. That's when I became aware how fast the cam,
lifters, and cylinders are lubed. It was intently. We evaluated different
bearing clearances as to the amount of oil put into suspension by the
crankshaft. The gears in the oil pump can be changed in just a few minutes.
That's when we studied the effects of the use of high volume oil pumps. Back
to cold starts Dennis. I like the larger molecules of mineral oils with the
1200 PPM of ZDDP over the smaller ones in synthetics. If your engine seals
are older. Synthetic molecules will tend to slip out easier. I favor the
10/30 that GM recommended. That's the weight that GM set up the oil filter
with related oil filter bypass to work the most effectively in their
engines. I'm not in favor of oil additives except for engines with a new
cam. There are lots of oil choices out there. You need to pick what you
think is best for you. My choice is a 10/30 that has a C rating. ( Diesel )
This is for 3 major reasons.1. C rated oils can handle oil contaminants
better than S rated oils. ( Gas ) Go pull the dipstick in a diesel. Pure
black. 2 C rated oils can withstand more heat than S rated oils. If you
get near C rated oil limits. Your engine was toast way before the
oil's limits.3 Diesel engines have compression ratios of around 20 to 1.
Our Olds gas engines are at 8.5. That's a load.4 I like the idea that I
can buy a C rated oil th!
at has everything my old tech engine needs. Including the 1200 PPM of
zinc. And it's reasonably priced.I trust GM with their recommendations for
their engines.
Some people recommend Synthetic oils in our old tech engines. I'd be
interested in their reasons. Maybe I'm missing something.I recommend
Synthetic oils also. But in new modern engines that the manufacture suggest.
Bob Dunahugh
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