| [GMCnet] Synthetic oil. Just some thoughts [message #282313] |
Fri, 17 July 2015 10:34  |
fbhtxak
Messages: 191
Registered: April 2006
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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:
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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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| Re: [GMCnet] Synthetic oil. Just some thoughts [message #282578 is a reply to message #282313] |
Mon, 20 July 2015 08:15  |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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There is one flaw in the Diesel loading on the bearings theory. Diesel truck engines have much larger surface areas to spread out the load and not break through the oil layer causing metal to metal contact.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] Synthetic oil. Just some thoughts [message #282627 is a reply to message #282313] |
Mon, 20 July 2015 13:45 |
fbhtxak
Messages: 191
Registered: April 2006
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Bob,
Like Bob de Kruyff, I am also a proponent of buying current API-spec engine
oils "at market"(including "house brands"), regardless of ZDDP
concentrations. For "old technology/flat tappet" engines beyond the
"break-in" stage (i.e., first 1000 miles or so), there is no documented
evidence that reduced ZDDP in modern dino engine oils has any deleterious
effect. That has been my experience in more than 100K miles on the OEM "403"
engine in my '78 Royale and the OEM "454" engine in my '82 Airstream.
Early-on in the paranoia about reduced ZDDP, I contacted engineering
associates in XOM's research and engineering labs for the "straight skinny"
on the effects of such in "old technology/flat tappet" engines. They
understandably represented that the performance of modern dino oils is much
superior to that of the "old technology/high ZDDP" oils. They, however, did
acknowledge an exception for "break-in" for new/rebuilt "old technology/flat
tappet" engines. They emphasized that during "break-in" for these engines,
oils with ZDDP levels of 14-1600 PPM must be used. After that, they observed
no benefit from continued use of the "old technology high ZDDP" oils
relative to oils designed for modern engines. As has often been acknowledged
on this forum, it is not uncommon for modern engines to have service lives
in excess of 300K mi. without a rebuild - a rarity for "old technology/flat
tappet engines using even the "old technology/high ZDDP" oils of yesteryear.
Fred
Fred B. Hudspeth
1978 Royale - Tyler, TX
1982 Airstream Excella 28' Mh - Cooper Landing, Alaska
Message: 6
Date: Mon, 20 Jul 2015 00:39:04 -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"
As long as that oil contains the proper ZDDP.
Bob de Kruyff has a simple oil change plan that really fits most GMC
situations.Well put.Bob Dunahugh.
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| Re: [GMCnet] Synthetic oil. Just some thoughts [message #282644 is a reply to message #282313] |
Mon, 20 July 2015 17:18 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Fred I agree. Paranoia sells product. At first any cam lobe failure was blamed on low ZDDP when there could be a number of reasons contributing to the failure. It's mostly about lifter foot pressures. High RPM muscle car engines benefit with ZDDP as they run steep cam ramps and strong springs to stop float. We do not (or should not) run those valve train styles. Worst you can do is add too much ZDDP as the phoshoric acid attacks and causes spalling at about 2000 PPM and above.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] Synthetic oil. Just some thoughts [message #282675 is a reply to message #282627] |
Tue, 21 July 2015 06:59 |
kerry pinkerton
Messages: 2565
Registered: July 2012
Location: Harvest, Al
Karma: 15
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Senior Member |
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fbhtxak wrote on Mon, 20 July 2015 13:45Like Bob de Kruyff, I am also a proponent of buying current API-spec engine oils "at market"(including "house brands"),...
Fred, what does 'at market' mean. Are you saying that you worry about the API spec and don't care about the brand as long as it meets the API-spec you want. If so, what API spec do YOU prefer?
Kerry Pinkerton - North Alabama
Had 5 over the years. Currently have a '06 Fleetwood Discovery 39L
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